Research on under-constrained problem for large-scale eccentric structure lifting
Received:February 24, 2019  Revised:July 29, 2019
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KeyWord:structure lifting  under-constrained  multibody system dynamics  virtual power equations
张树翠 安阳工学院 机械工程学院, 安阳
齐朝晖 大连理工大学 工程力学系 工业装备结构分析国家重点实验室, 大连
徐金帅 大连理工大学 工程力学系 工业装备结构分析国家重点实验室, 大连
张欣刚 大连理工大学 工程力学系 工业装备结构分析国家重点实验室, 大连
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      Levelness of the module is the key index during the lifting operation.Under most conditions,a counterweight is needed to meet the levelness requirement.If we use the classical FEM for lifting analysis,additional constraints are always needed to eliminate the rigid body displacement,moreover,if we want to determine the counterweight,we may need repetitive enforcement of the equations of equilibrium,and thus the computational efficiency would be unsatisfactory.To overcome these problems,the motion of the lifting module can be decomposed into the rigid-body motion of the body and the elastic motion relative to the rigid body motion.Hence,the under-constrained problem can be converted to a static equilibrium problems of a multibody systems.In the following,the equations of equilibrium for model forces and the tangent stiffness matrix are obtained based on the virtual power principle.Then,the counterweight is expressed as a function of the basic counterweight and the load factor.The equations of equilibrium can then be converted to a set of ordinary differential equations(ODEs).Using an efficient algorithm for the ODEs,the counterweight can be easily and quickly obtained.Numerical examples shows that the proposed method can be a new approach for under-constrained problems and possess a reasonable accuracy and relatively rapid speed to obtain the counterweight.