In this study,a modeling method for investigating the dynamic characteristics of a hydraulically driven shell manipulator with revolute clearance joints is presented.This model accounts for the effect of the clearance...In this study,a modeling method for investigating the dynamic characteristics of a hydraulically driven shell manipulator with revolute clearance joints is presented.This model accounts for the effect of the clearance,the flexibility of the rotating beam,and the coupled dynamic characteristics of the hydraulic cylinder.A modified contact force model was developed to simulate the physical properties of realistic revolute joints with small clearances,heavy loads,and variable contact stiffnesses and damping coefficients with variations of the indentations.Considering the strong coupling relationship between the hydraulic cylinder and the flexible beam,a system equation of motion combining the state variables of the hydraulic cylinder and mechanical system was established.The complex nonlinear friction force of the hydraulic cylinder motion was constructed using a modified Lu Gre model,and the parameters of the friction model were identified using intelligent identification algorithms.Moreover,a test system for the shell manipulator was established to achieve experimental validation.Finally,the effects of the clearance size and the stiffness of the cylinder support on the dynamic response were investigated.展开更多
The objective of this study is to investigate the effects of the Coulomb dry friction model versus the modified Coulomb friction model on the dynamic behavior of the slider-crank mechanism with a revolute clearance jo...The objective of this study is to investigate the effects of the Coulomb dry friction model versus the modified Coulomb friction model on the dynamic behavior of the slider-crank mechanism with a revolute clearance joint. The normal and tangential forces acting on the contact points between the journal and the bearing are described by using a Hertzian-based contact force model and the Coulomb friction models, respectively.The dynamic equations of the mechanism are derived based on the Lagrange equations of the first kind and the Baumgarte stabilization method. The frictional force is solved via the linear complementarity problem(LCP) algorithm and the trial-and-error algorithm.Finally, three numerical examples are given to show the influence of the two Coulomb friction models on the dynamic behavior of the mechanism. Numerical results show that due to the stick friction, the slider-crank mechanism may exhibit stick-slip motion and can balance at some special positions, while the mechanism with ideal joints cannot.展开更多
This paper presents a non-smooth multibody dynamic formulation and error analysis of an antenna pointing mechanism including frictional spatial revolute joints(FSRJs)with small clearance in the framework of the specia...This paper presents a non-smooth multibody dynamic formulation and error analysis of an antenna pointing mechanism including frictional spatial revolute joints(FSRJs)with small clearance in the framework of the special Euclidian group SE(3).The formulation leads to an inertial frame-invariant,a compact and unified description for rigid bodies and spatial revolute joints(SRJs).The geometric constraint of the bearing is covered by four open semi-cylinders,which can be treated as bilateral constraints assuming that the impact effects are negligible.The frictional contact problem is formulated as a horizontal linear complementary problem(HLCP),which is embedded in the Lie-group integration scheme.Error of the antenna pointing mechanism is modeled by means of the adjoint transformation and POE-based formula.The evolution of errors is obtained through the solution of non-smooth dynamics.The obtained numerical results illustrate the influences of FSRJs in dynamics modeling and error analysis of the antenna pointing mechanism.展开更多
The existence of the relative radial and axial movements of a revolute joint’s journal and bearing is widely known.The three-dimensional(3D)revolute joint model considers relative radial and axial clearances;therefor...The existence of the relative radial and axial movements of a revolute joint’s journal and bearing is widely known.The three-dimensional(3D)revolute joint model considers relative radial and axial clearances;therefore,the freedoms of motion and contact scenarios are more realistic than those of the two-dimensional model.This paper proposes a wear model that integrates the modeling of a 3D revolute clearance joint and the contact force and wear depth calculations.Time-varying contact stiffness is first considered in the contact force model.Also,a cycle-update wear depth calculation strategy is presented.A digital image correlation(DIC)non-contact measurement and a cylindricity test are conducted.The measurement results are compared with the numerical simulation,and the proposed model’s correctness and the wear depth calculation strategy are verified.The results show that the wear amount distribution on the bearing’s inner surface is uneven in the axial and radial directions due to the journal’s stochastic oscillations.The maximum wear depth locates where at the bearing’s edges the motion direction of the follower shifts.These find-ings help to seek the revolute joints’wear-prone parts and enhance their durability and reliability through improved design.展开更多
There are clearances in mechanism because of manufacture and assembly error,which reduces operation life and working accuracy of mechanism and has a great impact on dynamical responses.At the moment,research in this a...There are clearances in mechanism because of manufacture and assembly error,which reduces operation life and working accuracy of mechanism and has a great impact on dynamical responses.At the moment,research in this area mainly focuses on single degree⁃of⁃freedom mechanism considering one clearance,while research of multi⁃DOF mechanism considering multi⁃clearance is less.With the purpose of studying the dynamical characteristics of complex multi⁃DOF mechanism with multi⁃clearances,a dynamic model was developed.The dynamic responses of 2⁃DOF mechanism with two clearances under different positions,values,and numbers of clearance were analyzed.The displacement,velocity,acceleration,collision force,and the axis trajectory at clearance were then given.In addition,there is a limited amount of literature on chaotic phenomena,which mainly focuses on the chaotic phenomena of end⁃effector of mechanism.But in this paper,the non⁃linear characteristics were analyzed by chaotic phenomenon of clearance joint,then chaotic phenomenon was identified by Poincarémappings and phase diagrams.Bifurcation diagrams were given.The results will offer a reliable technical support for the study of dynamical responses of planar mechanisms and the analysis of chaotic phenomena.展开更多
Clearances in joints of a mechanical multibody system can induce impulsive forces, leading to vibrations that compromise the system’s reliability, stability, and lifespan. Through dynamic analysis, designers can inve...Clearances in joints of a mechanical multibody system can induce impulsive forces, leading to vibrations that compromise the system’s reliability, stability, and lifespan. Through dynamic analysis, designers can investigate the effects of the clearances on the dynamics of the multibody system. A revolute joint with clearance exhibits three motions which are;free-flight, impact and continuous contact motion modes. Therefore, a multibody system with n-number of revolute clearance joints will exhibit 3n motion modes which are a combination of the three motions in each joint. This study investigates experimentally the nine motion modes in a mechanical system with two revolute clearance joints. A slider crank mechanism has been used as the demonstrative example. We observed that the experimental curve exhibits a greater impact compared to the simulation curve. In conclusion, this experimental investigation offers valuable insights into the dynamics of planar mechanical systems with multiple clearance revolute joints. Utilizing a slider-crank mechanism for data acquisition, the study successfully confirmed seven out of nine motion modes previously identified in numerical research. The missing modes are attributed to inherent complexities in real-world systems, such as journal-bearing misalignment.展开更多
A stationary clearance link algorithm(SCLA)for calculating the reaction-force of revolute clearance joints in crank slider mechanisms is proposed in this paper.The SCLA is more efficient than other algorithms of the s...A stationary clearance link algorithm(SCLA)for calculating the reaction-force of revolute clearance joints in crank slider mechanisms is proposed in this paper.The SCLA is more efficient than other algorithms of the same accuracy.Furthermore,based on the Winkler foundation model,an unsymmetrical Winkler foundation model and a double elastic layer Winkler model are proposed.By integrating a dynamic model and the unsymmetrical Winkler foundation model with Archard wear model,an improved integrated wear prediction model is also generated.A series of experiments have been performed to compare with the predicted analysis data,and the results showed a good agreement.As a real industry application,with the double elastic layer Winkler model,the integrated wear prediction model was successfully used to predict the wear depth of the joint bearing(bimetallic bearing)for the cantilever crane of a concrete pump truck of Sany Heavy Industry.展开更多
As profound changes unseen in a century unfold at a faster pace,the world economy enters into a new phase of turbulence and transformation.Under the continuous impact of multiple shocks,the world economy is recovering...As profound changes unseen in a century unfold at a faster pace,the world economy enters into a new phase of turbulence and transformation.Under the continuous impact of multiple shocks,the world economy is recovering amidst twists and turns,with insufficient growth momentum and diverging development trends.Meanwhile,profound structural changes are reshaping the global economic landscape.A new round of technological revolution and industrial transformation,most notably the explosive development of disruptive technologies such as Artificial Intelligence(AI),is generating new industries,business models,and drivers of growth,while exerting far-reaching influence on the global division of labor,employment structures,and even international norms.展开更多
At this historic juncture of deepening technological revolution and industrial transformation,China's communication sector stands on the eve of another great leap forward.Reflecting on the development of communica...At this historic juncture of deepening technological revolution and industrial transformation,China's communication sector stands on the eve of another great leap forward.Reflecting on the development of communications over the past two decades,China has forged an innovative path from catching up to keeping pace and then to leading the way.Today,at the new starting point of 6G development and facing the paradigm shift brought about by“AI+communications,”China's scientific research community,with the courage to venture into uncharted territory,is advancing original theories such as the new communication paradigm based on a unified theoretical framework of information theory to the global forefront.展开更多
In recent years, the digital economy has become a key driver of deepening China-Thailand cooperation. As trade and industrial digitalization advance, artificial intelligence (AI), an essential force in the new wave of...In recent years, the digital economy has become a key driver of deepening China-Thailand cooperation. As trade and industrial digitalization advance, artificial intelligence (AI), an essential force in the new wave of technological revolution, is increasingly embedded in the bilateral agenda, steering collaboration beyond efficiencydriven “digital coordination” toward more structured and systemic“intelligent co-development.”Building on five decades of mutual trust since the establishment of diplomatic ties, this cooperation not only addresses the practical needs of industrial upgrading and governance transformation but offers a valuable reference for ASEAN countries exploring replicable pathways in the era of digital transformation.展开更多
AI,as a strategic technology leading the new round of scientific and technological revolution and industrial transformation,is profoundly reshaping people’s work and life.Chinese President Xi Jinping called for promo...AI,as a strategic technology leading the new round of scientific and technological revolution and industrial transformation,is profoundly reshaping people’s work and life.Chinese President Xi Jinping called for promoting a healthy and orderly development of AI during the 20th group study session of the Political Bureau of the Communist Party of China(CPC)Central Committee held on 25 April 2025.展开更多
0 INTRODUCTION Throughout human history,three major energy transitions have occurred:from burning wood in primitive times to using coal in 18th Century,then to oil and gas in 20th Century,and to the renewable energy r...0 INTRODUCTION Throughout human history,three major energy transitions have occurred:from burning wood in primitive times to using coal in 18th Century,then to oil and gas in 20th Century,and to the renewable energy revolution in the 21st Century(Zou et al.,2023).The three transitions have three characteristics in common:shifted from nonrenewable to renewable energy,from“resource-centric”to a“technology-centric”,and from“high-carbon fossil”to“net-zero”.展开更多
The ongoing revolution in information technology is reshaping human life. In the realm of health behavior, wearable technology emerges as a leading digital solution,capturing physical behaviors (i.e., physical activit...The ongoing revolution in information technology is reshaping human life. In the realm of health behavior, wearable technology emerges as a leading digital solution,capturing physical behaviors (i.e., physical activity, sedentary habits, sleep patterns) within the 24-h cycle of daily life. Wearables are applied in research, clinical practice, and as lifestyle devices;most obvious, they promise to be a key element for increasing human physical activity, one of the biggest health challenges nowadays.展开更多
1.Introduction Mobile communications have catalyzed a new era of informa-tion technology revolution,significantly broadening and deepen-ing human-to-human,human-to-machine,and machine-to-machine connections.With their...1.Introduction Mobile communications have catalyzed a new era of informa-tion technology revolution,significantly broadening and deepen-ing human-to-human,human-to-machine,and machine-to-machine connections.With their incredible speed of development and wide-reaching impact,mobile communications serve as the cornerstone of the Internet of Everything,profoundly reshaping human cognitive abilities and ways of thinking.Furthermore,mobile communications are altering the patterns of production and life,driving leaps in productivity quality,and strongly promot-ing innovation within human civilization.展开更多
Digital technology and the digital economy are at the forefront of the global technological revolution and industrial transformation.They are profoundly reshaping the international landscape of competition and restruc...Digital technology and the digital economy are at the forefront of the global technological revolution and industrial transformation.They are profoundly reshaping the international landscape of competition and restructuring the world economy.Major countries and economies around the globe are increasingly competing on digital technology and the digital economy,striving to secure a strategic advantage in the new round of international competition and establish a strong position in the evolving international order.展开更多
In the dynamic landscape of modern healthcare and precision medicine,the digital revolution is reshaping medical industries at an unprecedented pace,and traditional Chinese medicine(TCM)is no exception[1-4].The paper...In the dynamic landscape of modern healthcare and precision medicine,the digital revolution is reshaping medical industries at an unprecedented pace,and traditional Chinese medicine(TCM)is no exception[1-4].The paper“From digits towards digitization:the past,present,and future of traditional Chinese medicine”by Academician&TCM National Master Qi WANG(王琦).展开更多
基金supported by the National Natural Science Foundation of China [grant number 11472137]the Fundamental Research Funds for the Central Universities [grant numbers 309181A8801,30919011204]。
文摘In this study,a modeling method for investigating the dynamic characteristics of a hydraulically driven shell manipulator with revolute clearance joints is presented.This model accounts for the effect of the clearance,the flexibility of the rotating beam,and the coupled dynamic characteristics of the hydraulic cylinder.A modified contact force model was developed to simulate the physical properties of realistic revolute joints with small clearances,heavy loads,and variable contact stiffnesses and damping coefficients with variations of the indentations.Considering the strong coupling relationship between the hydraulic cylinder and the flexible beam,a system equation of motion combining the state variables of the hydraulic cylinder and mechanical system was established.The complex nonlinear friction force of the hydraulic cylinder motion was constructed using a modified Lu Gre model,and the parameters of the friction model were identified using intelligent identification algorithms.Moreover,a test system for the shell manipulator was established to achieve experimental validation.Finally,the effects of the clearance size and the stiffness of the cylinder support on the dynamic response were investigated.
基金Project supported by the National Natural Science Foundation of China(No.11772021)
文摘The objective of this study is to investigate the effects of the Coulomb dry friction model versus the modified Coulomb friction model on the dynamic behavior of the slider-crank mechanism with a revolute clearance joint. The normal and tangential forces acting on the contact points between the journal and the bearing are described by using a Hertzian-based contact force model and the Coulomb friction models, respectively.The dynamic equations of the mechanism are derived based on the Lagrange equations of the first kind and the Baumgarte stabilization method. The frictional force is solved via the linear complementarity problem(LCP) algorithm and the trial-and-error algorithm.Finally, three numerical examples are given to show the influence of the two Coulomb friction models on the dynamic behavior of the mechanism. Numerical results show that due to the stick friction, the slider-crank mechanism may exhibit stick-slip motion and can balance at some special positions, while the mechanism with ideal joints cannot.
基金supported by the National Natural Science Foundation of China(No.51635002 Key Program,52075016,U20A20281)。
文摘This paper presents a non-smooth multibody dynamic formulation and error analysis of an antenna pointing mechanism including frictional spatial revolute joints(FSRJs)with small clearance in the framework of the special Euclidian group SE(3).The formulation leads to an inertial frame-invariant,a compact and unified description for rigid bodies and spatial revolute joints(SRJs).The geometric constraint of the bearing is covered by four open semi-cylinders,which can be treated as bilateral constraints assuming that the impact effects are negligible.The frictional contact problem is formulated as a horizontal linear complementary problem(HLCP),which is embedded in the Lie-group integration scheme.Error of the antenna pointing mechanism is modeled by means of the adjoint transformation and POE-based formula.The evolution of errors is obtained through the solution of non-smooth dynamics.The obtained numerical results illustrate the influences of FSRJs in dynamics modeling and error analysis of the antenna pointing mechanism.
文摘The existence of the relative radial and axial movements of a revolute joint’s journal and bearing is widely known.The three-dimensional(3D)revolute joint model considers relative radial and axial clearances;therefore,the freedoms of motion and contact scenarios are more realistic than those of the two-dimensional model.This paper proposes a wear model that integrates the modeling of a 3D revolute clearance joint and the contact force and wear depth calculations.Time-varying contact stiffness is first considered in the contact force model.Also,a cycle-update wear depth calculation strategy is presented.A digital image correlation(DIC)non-contact measurement and a cylindricity test are conducted.The measurement results are compared with the numerical simulation,and the proposed model’s correctness and the wear depth calculation strategy are verified.The results show that the wear amount distribution on the bearing’s inner surface is uneven in the axial and radial directions due to the journal’s stochastic oscillations.The maximum wear depth locates where at the bearing’s edges the motion direction of the follower shifts.These find-ings help to seek the revolute joints’wear-prone parts and enhance their durability and reliability through improved design.
基金Sponsored by the Shandong Key Research and Development Public Welfare Program(Grant No.2019GGX104011)the Natural Science Foundation of Shandong Province(Grant No.ZR2017MEE066).
文摘There are clearances in mechanism because of manufacture and assembly error,which reduces operation life and working accuracy of mechanism and has a great impact on dynamical responses.At the moment,research in this area mainly focuses on single degree⁃of⁃freedom mechanism considering one clearance,while research of multi⁃DOF mechanism considering multi⁃clearance is less.With the purpose of studying the dynamical characteristics of complex multi⁃DOF mechanism with multi⁃clearances,a dynamic model was developed.The dynamic responses of 2⁃DOF mechanism with two clearances under different positions,values,and numbers of clearance were analyzed.The displacement,velocity,acceleration,collision force,and the axis trajectory at clearance were then given.In addition,there is a limited amount of literature on chaotic phenomena,which mainly focuses on the chaotic phenomena of end⁃effector of mechanism.But in this paper,the non⁃linear characteristics were analyzed by chaotic phenomenon of clearance joint,then chaotic phenomenon was identified by Poincarémappings and phase diagrams.Bifurcation diagrams were given.The results will offer a reliable technical support for the study of dynamical responses of planar mechanisms and the analysis of chaotic phenomena.
文摘Clearances in joints of a mechanical multibody system can induce impulsive forces, leading to vibrations that compromise the system’s reliability, stability, and lifespan. Through dynamic analysis, designers can investigate the effects of the clearances on the dynamics of the multibody system. A revolute joint with clearance exhibits three motions which are;free-flight, impact and continuous contact motion modes. Therefore, a multibody system with n-number of revolute clearance joints will exhibit 3n motion modes which are a combination of the three motions in each joint. This study investigates experimentally the nine motion modes in a mechanical system with two revolute clearance joints. A slider crank mechanism has been used as the demonstrative example. We observed that the experimental curve exhibits a greater impact compared to the simulation curve. In conclusion, this experimental investigation offers valuable insights into the dynamics of planar mechanical systems with multiple clearance revolute joints. Utilizing a slider-crank mechanism for data acquisition, the study successfully confirmed seven out of nine motion modes previously identified in numerical research. The missing modes are attributed to inherent complexities in real-world systems, such as journal-bearing misalignment.
基金supported by the National Natural Science Foundation of China(Grant No.51175409)
文摘A stationary clearance link algorithm(SCLA)for calculating the reaction-force of revolute clearance joints in crank slider mechanisms is proposed in this paper.The SCLA is more efficient than other algorithms of the same accuracy.Furthermore,based on the Winkler foundation model,an unsymmetrical Winkler foundation model and a double elastic layer Winkler model are proposed.By integrating a dynamic model and the unsymmetrical Winkler foundation model with Archard wear model,an improved integrated wear prediction model is also generated.A series of experiments have been performed to compare with the predicted analysis data,and the results showed a good agreement.As a real industry application,with the double elastic layer Winkler model,the integrated wear prediction model was successfully used to predict the wear depth of the joint bearing(bimetallic bearing)for the cantilever crane of a concrete pump truck of Sany Heavy Industry.
文摘As profound changes unseen in a century unfold at a faster pace,the world economy enters into a new phase of turbulence and transformation.Under the continuous impact of multiple shocks,the world economy is recovering amidst twists and turns,with insufficient growth momentum and diverging development trends.Meanwhile,profound structural changes are reshaping the global economic landscape.A new round of technological revolution and industrial transformation,most notably the explosive development of disruptive technologies such as Artificial Intelligence(AI),is generating new industries,business models,and drivers of growth,while exerting far-reaching influence on the global division of labor,employment structures,and even international norms.
文摘At this historic juncture of deepening technological revolution and industrial transformation,China's communication sector stands on the eve of another great leap forward.Reflecting on the development of communications over the past two decades,China has forged an innovative path from catching up to keeping pace and then to leading the way.Today,at the new starting point of 6G development and facing the paradigm shift brought about by“AI+communications,”China's scientific research community,with the courage to venture into uncharted territory,is advancing original theories such as the new communication paradigm based on a unified theoretical framework of information theory to the global forefront.
文摘In recent years, the digital economy has become a key driver of deepening China-Thailand cooperation. As trade and industrial digitalization advance, artificial intelligence (AI), an essential force in the new wave of technological revolution, is increasingly embedded in the bilateral agenda, steering collaboration beyond efficiencydriven “digital coordination” toward more structured and systemic“intelligent co-development.”Building on five decades of mutual trust since the establishment of diplomatic ties, this cooperation not only addresses the practical needs of industrial upgrading and governance transformation but offers a valuable reference for ASEAN countries exploring replicable pathways in the era of digital transformation.
文摘AI,as a strategic technology leading the new round of scientific and technological revolution and industrial transformation,is profoundly reshaping people’s work and life.Chinese President Xi Jinping called for promoting a healthy and orderly development of AI during the 20th group study session of the Political Bureau of the Communist Party of China(CPC)Central Committee held on 25 April 2025.
基金supported by the National Natural Science Foundation of China“Quantitative characterization of lacustrine shale oil mobility based on nano-scale oil-rock interactions”(No.42172180)Science and Technology Research Project for the China National Petroleum Corporation“Source-reservoir characteristics and sweet spot evaluation for terrestrial shale oil in China”(No.2021DJ1802)。
文摘0 INTRODUCTION Throughout human history,three major energy transitions have occurred:from burning wood in primitive times to using coal in 18th Century,then to oil and gas in 20th Century,and to the renewable energy revolution in the 21st Century(Zou et al.,2023).The three transitions have three characteristics in common:shifted from nonrenewable to renewable energy,from“resource-centric”to a“technology-centric”,and from“high-carbon fossil”to“net-zero”.
基金funded in part by the German Research Foundation(Grant reference:496846758).
文摘The ongoing revolution in information technology is reshaping human life. In the realm of health behavior, wearable technology emerges as a leading digital solution,capturing physical behaviors (i.e., physical activity, sedentary habits, sleep patterns) within the 24-h cycle of daily life. Wearables are applied in research, clinical practice, and as lifestyle devices;most obvious, they promise to be a key element for increasing human physical activity, one of the biggest health challenges nowadays.
基金supported by the National Key Research and Develop-ment Program of China(2019YFB1803400).
文摘1.Introduction Mobile communications have catalyzed a new era of informa-tion technology revolution,significantly broadening and deepen-ing human-to-human,human-to-machine,and machine-to-machine connections.With their incredible speed of development and wide-reaching impact,mobile communications serve as the cornerstone of the Internet of Everything,profoundly reshaping human cognitive abilities and ways of thinking.Furthermore,mobile communications are altering the patterns of production and life,driving leaps in productivity quality,and strongly promot-ing innovation within human civilization.
文摘Digital technology and the digital economy are at the forefront of the global technological revolution and industrial transformation.They are profoundly reshaping the international landscape of competition and restructuring the world economy.Major countries and economies around the globe are increasingly competing on digital technology and the digital economy,striving to secure a strategic advantage in the new round of international competition and establish a strong position in the evolving international order.
文摘In the dynamic landscape of modern healthcare and precision medicine,the digital revolution is reshaping medical industries at an unprecedented pace,and traditional Chinese medicine(TCM)is no exception[1-4].The paper“From digits towards digitization:the past,present,and future of traditional Chinese medicine”by Academician&TCM National Master Qi WANG(王琦).
