The condition of rotor system must be assessed in order to develop condition-based maintenance for rotating machinery. It is determined by multiple variables such as unbalance degree, misalignment degree, the amount o...The condition of rotor system must be assessed in order to develop condition-based maintenance for rotating machinery. It is determined by multiple variables such as unbalance degree, misalignment degree, the amount of bending deformation of the shaft, occurrence of shaft crack of rotor system and so on. The estimation of the degrees of unbalance and misalignment in flexible coupling-rotor system is discussed. The model-based approach is employed to solve this problem. The models of the equivalent external loads for unbalance and misalignment are derived and analyzed. Then, the degrees of unbalance and misalignment are estimated by analyzing the components of the equivalent external loads of which the frequencies are equal to the 1 and 2 times running frequency respectively. The equivalent external loads are calculated according to the dynamic equation of the original rotor system and the differences between the dynamical responses in normal case and the vibrations when the degree of unbalance or misalignment or both changes. The denoise method based on bandpass filter is used to decrease the effect of noise on the estimation accuracy. The numerical examples are given to show that the proposed approach can estimate the degrees of unbalance and misalignment of the flexible coupling-rotor system accurately.展开更多
The rigid flexible coupling system with a mass at non-tip position of the flexible beam is studied in this paper. Using the theory about mechanics problems in a non-inertial coordinate sys- tem, the dynamic equations ...The rigid flexible coupling system with a mass at non-tip position of the flexible beam is studied in this paper. Using the theory about mechanics problems in a non-inertial coordinate sys- tem, the dynamic equations of the rigid flexible coupling system with dynamic stiffening are estab- lished. It is clearly elucidated for the first time that, dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beam and the transverse vibration deformation of the beam. The modeling approach in this paper successfully solves problems of popular modeling methods nowadays： the derivation process is too complex by using only one dynamic principle; a clearly theoretical mechanism for dynamic stiffening can＇ t be offered. First, the mass at non-tip po- sition is incorporated into the continuous dynamic equations of the system by use of the Dirac lunch tion and the Heaviside function. Then, based on the conclusions of orthogonalization about the nor- mal constrained modes, the finite dimensional state space equations suitable for controller design are obtained. The numerical simulation results show that： dynamic stiffening is included in the first-or- der model established in this paper, which indicates the dynamic responses of the rigid flexible cou- pling system with large overall motion accurately. The results also show that the mass has a soften- ing effect on the dynamic behavior of the flexible beam, and the effect would be more obvious when the mass has a larger mass, or lies closer to the tip of the beam.展开更多
In a fusion reactor, the edge localized mode（ELM） coil has a mitigating effect on the ELMs of the plasma. The coil is placed close to the plasma between the vacuum vessel and the blanket to reduce its design power a...In a fusion reactor, the edge localized mode（ELM） coil has a mitigating effect on the ELMs of the plasma. The coil is placed close to the plasma between the vacuum vessel and the blanket to reduce its design power and improve its mitigating ability. The coil works in a high-temperature,high-nuclear-heat and high-magnetic-field environment. Due to the existence of outer superconducting coils, the coil is subjected to an alternating electromagnetic force induced by its own alternating current and the outer magnetic field. The design goal for the ELM coil is to maintain its structural integrity in the multi-physical field. Taking as an example the middle ELM coil（with flexible supports） of ITER（the International Thermonuclear Fusion Reactor）, an electromagnetic–thermal–structural coupling analysis is carried out using ANSYS. The results show that the flexible supports help the three-layer casing meet the static and fatigue design requirements. The structural design of the middle ELM coil is reasonable and feasible. The work described in this paper provides the theoretical basis and method for ELM coil design.展开更多
A rigid flexible coupling physical model which can represent a flexible spacecraft is investigated in this paper. By applying the mechanics theory in a non-inertial coordinate system,the rigid flexible coupling dynami...A rigid flexible coupling physical model which can represent a flexible spacecraft is investigated in this paper. By applying the mechanics theory in a non-inertial coordinate system,the rigid flexible coupling dynamic model with dynamic stiffening is established via the subsystemmodeling framework. It is clearly elucidated for the first time that,dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beamand the transverse vibration deformation of the beam. The modeling approach in this paper successfully avoids problems which are caused by other popular modeling methods nowadays： the derivation process is too complex by using only one dynamic principle; a clearly theoretical explanation for dynamic stiffening can＇t be provided. First,the continuous dynamic models of the flexible beamand the central rigid body are established via structural dynamics and angular momentumtheory respectively. Then,based on the conclusions of orthogonalization about the normal constrained modes,the finite dimensional dynamic model suitable for controller design is obtained. The numerical simulation validations showthat： dynamic stiffening is successfully incorporated into the dynamic characteristics of the first-order model established in this paper,which can indicate the dynamic responses of the rigid flexible coupling system with large overall motion accurately,and has a clear modeling mechanism,concise expressions and a good convergence.展开更多
In order to meet the urgent need for diversified and multi-functional deployable antennas in many major national aerospace projects,such as interstellar exploration,the fourth phase of lunar exploration project,and th...In order to meet the urgent need for diversified and multi-functional deployable antennas in many major national aerospace projects,such as interstellar exploration,the fourth phase of lunar exploration project,and the industrial application of Bei Dou,a deployable antenna structure composed of hexagonal prism and pentagonal prism modules is proposed.Firstly,the arrangement and combination rules of pentagonal prism and hexagonal prism modules on the plane were analyzed.Secondly,the spatial geometric model of the deployable antenna composed of pentagonal prism and hexagonal prism modules was established.The influence of module size on the antenna shape was then analyzed,and the kinematic model of the deployable antenna established by coordinate transformation.Finally,the above model was verified using MATLAB software.The simulation results showed that the proposed modular deployable antenna structure can realize accurate connection between modules,complete the expected deployment and folding functional requirements.It is hoped that this research can provide reference for the basic research and engineering application of deployable antennas in China.展开更多
In rotor dynamics,blades are normally modelled as a slender beam,in which elastic deformations are coupled with each other.To identify these coupling effects,new rigid-flexible structural model for helicopter rotor sy...In rotor dynamics,blades are normally modelled as a slender beam,in which elastic deformations are coupled with each other.To identify these coupling effects,new rigid-flexible structural model for helicopter rotor system is proposed in this paper.Finite rotations of the whole blade(on flapwise,lagwise,and torsional)are described as three global rigid degrees of freedom.The nonlinear deformation geometrics of the beam is built on geometrically exact beam theory.New expressions for blade strain energy,kinetic energy,and virtual work of various kinds of external forces are derived as functions of finite rotations and elastic deformations.To quantify the coupling characteristics,following the definition of coupling factor in electromagnetics,a new coupling factor between two modal components on each mode is introduced in modal analysis.Simulations show that the new structural model is highly capable of solving static and dynamic problems in rotor system and the maximum deformation that moderate deformation beam theory can predict might be 15%of beam length.After the new coupling factor is applied to study structurally coupled characteristics of rotor blade,it can be concluded that closeness of natural frequencies likely indicates considerable coupling between corresponding DOFs in structure.展开更多
The flight-structural dynamics of a high-aspect-ratio wing challenge the flight control design.This paper develops a reduced model of coupled dynamics with stability consideration.The structural dynamics are formulate...The flight-structural dynamics of a high-aspect-ratio wing challenge the flight control design.This paper develops a reduced model of coupled dynamics with stability consideration.The structural dynamics are formulated with dihedrals,and the central loads drive the deformation.The control-oriented model with essential coupled dynamics is formulated.Modal sensitivity anal-ysis and input–output pairing are performed to identify the control structure.Besides,an example of flight control design is provided to discuss the necessity of considering structural dynamics in controller design.Analytical coupled flight dynamics provide a system-theoretic approach for sta-bility and facilitate model-based control techniques.Simulation results reveal the characteristics of flight-structural coupled dynamics and demonstrate that the influence of flexible modes should be considered in control design,especially in lateral dynamics.展开更多
A rigid flexible coupled system which consists of a central rigid body deploying a flexible appendage is considered. The appendage is modeled as a finite deflection beam having linear constitutive equations....A rigid flexible coupled system which consists of a central rigid body deploying a flexible appendage is considered. The appendage is modeled as a finite deflection beam having linear constitutive equations. By taking the energy integral as Lyapunov function, it is proved that nonlinear transverse vibrations of the beam undergoing uniform extension or retrieval are stable when there are not controlling moment in the central rigid body and driving force on the beam, according to the partial stable theorem.展开更多
Based on its prototype of machine-isolator-foundation systems, a theoretical model for dynamic coupled linear system is established, in which both the passive and active control factors are considered. Power flow is u...Based on its prototype of machine-isolator-foundation systems, a theoretical model for dynamic coupled linear system is established, in which both the passive and active control factors are considered. Power flow is used as the cost function to evaluate the isolation effectiveness. And the transmission of vibratory power flow from a vibrating rigid body into a simply supported thin panel through passive isolators and actuators is investigated numerically. The active control strategy is summarized in the conclusion.展开更多
基金supported by National Natural Science Foundation of China(Grant No. 10772061)Heilongjiang Provincial Natural Science Foundation of China(Grant No. ZJG0704)
文摘The condition of rotor system must be assessed in order to develop condition-based maintenance for rotating machinery. It is determined by multiple variables such as unbalance degree, misalignment degree, the amount of bending deformation of the shaft, occurrence of shaft crack of rotor system and so on. The estimation of the degrees of unbalance and misalignment in flexible coupling-rotor system is discussed. The model-based approach is employed to solve this problem. The models of the equivalent external loads for unbalance and misalignment are derived and analyzed. Then, the degrees of unbalance and misalignment are estimated by analyzing the components of the equivalent external loads of which the frequencies are equal to the 1 and 2 times running frequency respectively. The equivalent external loads are calculated according to the dynamic equation of the original rotor system and the differences between the dynamical responses in normal case and the vibrations when the degree of unbalance or misalignment or both changes. The denoise method based on bandpass filter is used to decrease the effect of noise on the estimation accuracy. The numerical examples are given to show that the proposed approach can estimate the degrees of unbalance and misalignment of the flexible coupling-rotor system accurately.
文摘The rigid flexible coupling system with a mass at non-tip position of the flexible beam is studied in this paper. Using the theory about mechanics problems in a non-inertial coordinate sys- tem, the dynamic equations of the rigid flexible coupling system with dynamic stiffening are estab- lished. It is clearly elucidated for the first time that, dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beam and the transverse vibration deformation of the beam. The modeling approach in this paper successfully solves problems of popular modeling methods nowadays： the derivation process is too complex by using only one dynamic principle; a clearly theoretical mechanism for dynamic stiffening can＇ t be offered. First, the mass at non-tip po- sition is incorporated into the continuous dynamic equations of the system by use of the Dirac lunch tion and the Heaviside function. Then, based on the conclusions of orthogonalization about the nor- mal constrained modes, the finite dimensional state space equations suitable for controller design are obtained. The numerical simulation results show that： dynamic stiffening is included in the first-or- der model established in this paper, which indicates the dynamic responses of the rigid flexible cou- pling system with large overall motion accurately. The results also show that the mass has a soften- ing effect on the dynamic behavior of the flexible beam, and the effect would be more obvious when the mass has a larger mass, or lies closer to the tip of the beam.
基金the Province Postdoctoral Foundation of Jiangsu(1501164B)the Technical Innovation Nurturing Foundation of Yangzhou University(2015CXJ016)China Postdoctoral Science Foundation(2016M600447)
文摘In a fusion reactor, the edge localized mode（ELM） coil has a mitigating effect on the ELMs of the plasma. The coil is placed close to the plasma between the vacuum vessel and the blanket to reduce its design power and improve its mitigating ability. The coil works in a high-temperature,high-nuclear-heat and high-magnetic-field environment. Due to the existence of outer superconducting coils, the coil is subjected to an alternating electromagnetic force induced by its own alternating current and the outer magnetic field. The design goal for the ELM coil is to maintain its structural integrity in the multi-physical field. Taking as an example the middle ELM coil（with flexible supports） of ITER（the International Thermonuclear Fusion Reactor）, an electromagnetic–thermal–structural coupling analysis is carried out using ANSYS. The results show that the flexible supports help the three-layer casing meet the static and fatigue design requirements. The structural design of the middle ELM coil is reasonable and feasible. The work described in this paper provides the theoretical basis and method for ELM coil design.
文摘A rigid flexible coupling physical model which can represent a flexible spacecraft is investigated in this paper. By applying the mechanics theory in a non-inertial coordinate system,the rigid flexible coupling dynamic model with dynamic stiffening is established via the subsystemmodeling framework. It is clearly elucidated for the first time that,dynamic stiffening is produced by the coupling effect of the centrifugal inertial load distributed on the beamand the transverse vibration deformation of the beam. The modeling approach in this paper successfully avoids problems which are caused by other popular modeling methods nowadays： the derivation process is too complex by using only one dynamic principle; a clearly theoretical explanation for dynamic stiffening can＇t be provided. First,the continuous dynamic models of the flexible beamand the central rigid body are established via structural dynamics and angular momentumtheory respectively. Then,based on the conclusions of orthogonalization about the normal constrained modes,the finite dimensional dynamic model suitable for controller design is obtained. The numerical simulation validations showthat： dynamic stiffening is successfully incorporated into the dynamic characteristics of the first-order model established in this paper,which can indicate the dynamic responses of the rigid flexible coupling system with large overall motion accurately,and has a clear modeling mechanism,concise expressions and a good convergence.
文摘In order to meet the urgent need for diversified and multi-functional deployable antennas in many major national aerospace projects,such as interstellar exploration,the fourth phase of lunar exploration project,and the industrial application of Bei Dou,a deployable antenna structure composed of hexagonal prism and pentagonal prism modules is proposed.Firstly,the arrangement and combination rules of pentagonal prism and hexagonal prism modules on the plane were analyzed.Secondly,the spatial geometric model of the deployable antenna composed of pentagonal prism and hexagonal prism modules was established.The influence of module size on the antenna shape was then analyzed,and the kinematic model of the deployable antenna established by coordinate transformation.Finally,the above model was verified using MATLAB software.The simulation results showed that the proposed modular deployable antenna structure can realize accurate connection between modules,complete the expected deployment and folding functional requirements.It is hoped that this research can provide reference for the basic research and engineering application of deployable antennas in China.
文摘In rotor dynamics,blades are normally modelled as a slender beam,in which elastic deformations are coupled with each other.To identify these coupling effects,new rigid-flexible structural model for helicopter rotor system is proposed in this paper.Finite rotations of the whole blade(on flapwise,lagwise,and torsional)are described as three global rigid degrees of freedom.The nonlinear deformation geometrics of the beam is built on geometrically exact beam theory.New expressions for blade strain energy,kinetic energy,and virtual work of various kinds of external forces are derived as functions of finite rotations and elastic deformations.To quantify the coupling characteristics,following the definition of coupling factor in electromagnetics,a new coupling factor between two modal components on each mode is introduced in modal analysis.Simulations show that the new structural model is highly capable of solving static and dynamic problems in rotor system and the maximum deformation that moderate deformation beam theory can predict might be 15%of beam length.After the new coupling factor is applied to study structurally coupled characteristics of rotor blade,it can be concluded that closeness of natural frequencies likely indicates considerable coupling between corresponding DOFs in structure.
基金co-supported by the Natural Science Founda-tion of Jiangsu Province,China(No.BK20200437)the National Natural Science Foundation of China(No.62103187)the Fundamental Research Funds for the Cen-tral Universities,China(No.NT2022025).
文摘The flight-structural dynamics of a high-aspect-ratio wing challenge the flight control design.This paper develops a reduced model of coupled dynamics with stability consideration.The structural dynamics are formulated with dihedrals,and the central loads drive the deformation.The control-oriented model with essential coupled dynamics is formulated.Modal sensitivity anal-ysis and input–output pairing are performed to identify the control structure.Besides,an example of flight control design is provided to discuss the necessity of considering structural dynamics in controller design.Analytical coupled flight dynamics provide a system-theoretic approach for sta-bility and facilitate model-based control techniques.Simulation results reveal the characteristics of flight-structural coupled dynamics and demonstrate that the influence of flexible modes should be considered in control design,especially in lateral dynamics.
文摘A rigid flexible coupled system which consists of a central rigid body deploying a flexible appendage is considered. The appendage is modeled as a finite deflection beam having linear constitutive equations. By taking the energy integral as Lyapunov function, it is proved that nonlinear transverse vibrations of the beam undergoing uniform extension or retrieval are stable when there are not controlling moment in the central rigid body and driving force on the beam, according to the partial stable theorem.
文摘Based on its prototype of machine-isolator-foundation systems, a theoretical model for dynamic coupled linear system is established, in which both the passive and active control factors are considered. Power flow is used as the cost function to evaluate the isolation effectiveness. And the transmission of vibratory power flow from a vibrating rigid body into a simply supported thin panel through passive isolators and actuators is investigated numerically. The active control strategy is summarized in the conclusion.
