The linear multibody system transfer matrix method(LMSTMM)provides a powerful tool for analyzing the vibration characteristics of a mechanical system.However,the original LMSTMM cannot resolve the eigenvalues of the s...The linear multibody system transfer matrix method(LMSTMM)provides a powerful tool for analyzing the vibration characteristics of a mechanical system.However,the original LMSTMM cannot resolve the eigenvalues of the systems with ideal hinges(i.e.,revolute hinge,sliding hinge,spherical hinge,cylindrical hinge,etc.)or bodies under conservative forces due to the lack of the corresponding transfer matrices.This paper enables the LMSTMM to solve the eigenvalues of the planar multibody systems with ideal hinges or rigid bodies under conservative forces.For a rigid body,the transfer matrix can now consider coupling terms between forces and kinematic state perturbations.Also,conservative forces that contribute to the eigenvalues can be considered.Meanwhile,ideal hinges are introduced to LMSTMM,which enables the treatment of eigenvalues of general multibody systems using LMSTMM.Finally,the comparative analysis with ADAMS software and analytical solutions verifies the effectiveness of the proposed approach in this paper.展开更多
Generalized short circuit ratio(g SCR)for grid strength assessment of multi-infeed high-voltage direct current(MIDC)systems is a rigorous theoretical extension of the traditional SCR,which enables SCR to be extended t...Generalized short circuit ratio(g SCR)for grid strength assessment of multi-infeed high-voltage direct current(MIDC)systems is a rigorous theoretical extension of the traditional SCR,which enables SCR to be extended to MIDC systems.However,g SCR is originally based on the assumption of homogeneous MIDC systems,in which all high-voltage direct current(HVDC)converters have an identical control configuration,thus presenting challenges to applications of g SCR to inhomogeneous MIDC systems.To weaken this assumption,this paper applies matrix perturbation theory to explore the possibility of utilization of g SCR into inhomogeneous MIDC systems.Results of numerical experiments show that in inhomogeneous MIDC systems,the previously proposed g SCR can still be used without modification.However,critical g SCR(Cg SCR)must be redefined by considering the characteristics of control configurations of HVDC converter.Accordingly,the difference between g SCR and redefined Cg SCR can effectively quantify the pertinent AC grid strength in terms of the static-voltage stability margin.The performance of the proposed method is demonstrated in a triple-infeed inhomogeneous line commutated converter based high-voltage direct current(LCC-HVDC)system.展开更多
A new method for structural damage identification is presented based on perturbations of curvature mode shape and frequency.Firstly,the structure's mass and stiffness matrices are expressed as functions of its ele...A new method for structural damage identification is presented based on perturbations of curvature mode shape and frequency.Firstly,the structure's mass and stiffness matrices are expressed as functions of its elements'physical parameters,which reflect their damage states. According to differences in the curvature mode shape of the structure in undamaged and damaged states,possible damage equations and determined damage equations are established and used to solve for the elements'damage parameters.Then,to ensure the accuracy of the recognition result,a reasonable solution is substituted into a damage-checking equation based on the change of frequency of the damaged structure.Numerical examples are used to show that,to identify the damage,only one order mode needs to be tested.When the degree of damage is low, first-order perturbation equations can be used to recognize the damage with sufficient accuracy. If the extent of the damage is high,second-order perturbation equations can be used to provide more accurate identification results.展开更多
基金Natural Science Foundation of Jiangsu Province,Grant/Award Number:BK20190438National Natural Science Foundation of China,Grant/Award Number:11902158。
文摘The linear multibody system transfer matrix method(LMSTMM)provides a powerful tool for analyzing the vibration characteristics of a mechanical system.However,the original LMSTMM cannot resolve the eigenvalues of the systems with ideal hinges(i.e.,revolute hinge,sliding hinge,spherical hinge,cylindrical hinge,etc.)or bodies under conservative forces due to the lack of the corresponding transfer matrices.This paper enables the LMSTMM to solve the eigenvalues of the planar multibody systems with ideal hinges or rigid bodies under conservative forces.For a rigid body,the transfer matrix can now consider coupling terms between forces and kinematic state perturbations.Also,conservative forces that contribute to the eigenvalues can be considered.Meanwhile,ideal hinges are introduced to LMSTMM,which enables the treatment of eigenvalues of general multibody systems using LMSTMM.Finally,the comparative analysis with ADAMS software and analytical solutions verifies the effectiveness of the proposed approach in this paper.
基金jointly supported by the National Natural Science Foundation of China(No.52007163)China Postdoctoral Science Foundation(No.2020M671718)。
文摘Generalized short circuit ratio(g SCR)for grid strength assessment of multi-infeed high-voltage direct current(MIDC)systems is a rigorous theoretical extension of the traditional SCR,which enables SCR to be extended to MIDC systems.However,g SCR is originally based on the assumption of homogeneous MIDC systems,in which all high-voltage direct current(HVDC)converters have an identical control configuration,thus presenting challenges to applications of g SCR to inhomogeneous MIDC systems.To weaken this assumption,this paper applies matrix perturbation theory to explore the possibility of utilization of g SCR into inhomogeneous MIDC systems.Results of numerical experiments show that in inhomogeneous MIDC systems,the previously proposed g SCR can still be used without modification.However,critical g SCR(Cg SCR)must be redefined by considering the characteristics of control configurations of HVDC converter.Accordingly,the difference between g SCR and redefined Cg SCR can effectively quantify the pertinent AC grid strength in terms of the static-voltage stability margin.The performance of the proposed method is demonstrated in a triple-infeed inhomogeneous line commutated converter based high-voltage direct current(LCC-HVDC)system.
基金National Natural Science Foundation of China (No.11402090)Key Scientific Research Projects in Colleges and Universities of Henan Province (No.17B130001,No.19A560014)Science and Technology Project of Henan Province (No.182102310890).
文摘A new method for structural damage identification is presented based on perturbations of curvature mode shape and frequency.Firstly,the structure's mass and stiffness matrices are expressed as functions of its elements'physical parameters,which reflect their damage states. According to differences in the curvature mode shape of the structure in undamaged and damaged states,possible damage equations and determined damage equations are established and used to solve for the elements'damage parameters.Then,to ensure the accuracy of the recognition result,a reasonable solution is substituted into a damage-checking equation based on the change of frequency of the damaged structure.Numerical examples are used to show that,to identify the damage,only one order mode needs to be tested.When the degree of damage is low, first-order perturbation equations can be used to recognize the damage with sufficient accuracy. If the extent of the damage is high,second-order perturbation equations can be used to provide more accurate identification results.
