An element coupling model (ECM) method was proposed to simulate the global behavior and local damage of a structure.In order to reflect the local damage and improve the computational efficiency,three-dimensional (3D) ...An element coupling model (ECM) method was proposed to simulate the global behavior and local damage of a structure.In order to reflect the local damage and improve the computational efficiency,three-dimensional (3D) solid elements and one-dimensional (1D) beam element were coupled by the multi-point constraint equations.A reduced scale 1?8 model test was simulated by the ECM and a full three dimensional model (3DM) contrastively.The results show that the global behavior and local damages of ECM agree well with the test and 3DM.It is indicated that the proposed method can be used in the structural nonlinear analysis accurately and efficiently.展开更多
When the tunneling boring machine(TBM) cutterhead tunnels, the excessive vibration and damage are a severe engineering problem, thereby the anti-vibration design is a key technology in the disc cutter system. The stru...When the tunneling boring machine(TBM) cutterhead tunnels, the excessive vibration and damage are a severe engineering problem, thereby the anti-vibration design is a key technology in the disc cutter system. The structure of disc cutter contains many joint interfaces among cutter ring, cutter body, bearings and cutter shaft. On account of the coupling for dynamic contact and the transfer path among joint interface, mechanical behavior of disc cutter becomes extremely complex under the impact of heavy-duty, which puts forward higher requirements for disc cutter design. A multi-degree-of-freedom coupling dynamic model, which contains a cutter ring, a cutter body, two bearings and cutter shaft, is established, considering the external stochastic excitations, bearing nonlinear contact force, multidirectional mutual coupling vibration, etc. Based on the parameters of an actual project and the strong impact external excitations, the modal properties and dynamic responses are analyzed, as well as the cutter shaft and bearings' loads and load transmission law are obtained. Numerical results indicate the maximum radial and axial cutter ring amplitudes of dynamic responses are 0.568 mm and 0.112 mm; the maximum radial and axial vibration velocities are 41.1 mm/s and 38.9 mm/s; the maximum radial and axial vibration accelerations are 94.7 m/s2 and 58.6 m/s2; the maximum swing angle and angular velocity of cutter ring are 0.007° and 0.0074 rad/s, respectively. Finally, the maximum load of bearing roller is 40.3 k N. The proposed research lays a foundation for structure optimization design of disc cutter and cutter base, as well as model selection, modification and fatigue life of the cutter bearing.展开更多
In order to improve the trajectory tracking precision and reduce the synchronization error of a 6-DOF lightweight robot, nonlinear proportion-deviation （N-PD） cross-coupling synchronization control strategy based on...In order to improve the trajectory tracking precision and reduce the synchronization error of a 6-DOF lightweight robot, nonlinear proportion-deviation （N-PD） cross-coupling synchronization control strategy based on adjacent coupling error analysis is presented. The mathematical models of the robot, including kinematic model, dynamic model and spline trajectory planing, are established and verified. Since it is difficult to describe the real-time contour error of the robot for complex trajectory, the adjacent coupling error is analyzed to solve the problem. Combined with nonlinear control and coupling performance of the robot, N-PD cross-coupling synchronization controller is designed and validated by simulation analysis. A servo control experimental system which mainly consists of laser tracking system, the robot mechanical system and EtherCAT based servo control system is constructed. The synchronization error is significantly decreased and the maximum trajectory error is reduced from 0.33 mm to 0.1 mm. The effectiveness of the control algorithm is validated by the experimental results, thus the control strategy can improve the robot＇s trajectory tracking precision significantly.展开更多
A model of vibrating device coupling two pendulums (VDP) which is highly nonlinear was put forward to conduct vibration analysis. Based on energy analysis, dynamic equations with cubic nonlinearities were established ...A model of vibrating device coupling two pendulums (VDP) which is highly nonlinear was put forward to conduct vibration analysis. Based on energy analysis, dynamic equations with cubic nonlinearities were established using Lagrange's equation. In order to obtain approximate solution, multiple time scales method, one of perturbation technique, was applied. Cases of non-resonant and 1:1:2:2 internal resonant were discussed. In the non-resonant case, the validity of multiple time scales method is confirmed, comparing numerical results derived from fourth order Runge-Kutta method with analytical results derived from first order approximate expression. In the 1:1:2:2 internal resonant case, modal amplitudes of Aa1 and Ab2 increase, respectively, from 0.38 to 0.63 and from 0.19 to 0.32, while the corresponding frequencies have an increase of almost 1.6 times with changes of initial conditions, indicating the existence of typical nonlinear phenomenon. In addition, the chaotic motion is found under this condition.展开更多
A class of chaotic map called piecewise-quadratic-equation map to design feedback stream cipher is proposed. Such map can generate chaotic signals that have uniform distribution function, δ-like autocorrelation funct...A class of chaotic map called piecewise-quadratic-equation map to design feedback stream cipher is proposed. Such map can generate chaotic signals that have uniform distribution function, δ-like autocorrelation function. Compared with the piecewise-linear map, this map provides enhanced security in that they can maintain the original perfect statistical properties, as well as overcome the defect of piecewise-linearity and expand the key space. This paper presents a scheme to improve the local complexity of the chaotic stream cipher based on the piecewise-quadratic-equationmap. Both the theoretic analysis and the results of simulation show that this scheme improves the microstructure of the phase-space graph on condition that the good properties of the original scheme are remained.展开更多
为保障国家能源安全,近年来国家加大了对压缩空气储能技术的研发投入,这类工程较以往常规工程情况更为复杂,岩石的应力松弛特性也会受更多因素影响。针对压缩空气储能工程特点,从新研究角度出发,进行了气压-应力耦合作用下盐岩应力松弛...为保障国家能源安全,近年来国家加大了对压缩空气储能技术的研发投入,这类工程较以往常规工程情况更为复杂,岩石的应力松弛特性也会受更多因素影响。针对压缩空气储能工程特点,从新研究角度出发,进行了气压-应力耦合作用下盐岩应力松弛试验,探究不同气压、轴向启动应力条件下盐岩的应力松弛特性。结果表明:(1)盐岩的应力松弛宏观规律不受气压影响,气压-应力耦合作用下盐岩的应力松弛仍可划分为快速、减速、稳定松弛3个阶段。其中,快速松弛阶段的松弛量占整体松弛量50%左右,而稳定松弛阶段在整个松弛过程中占比最大;(2)盐岩应力松弛受轴向启动应力和气压影响,轴向启动应力和气压越高,应力松弛初速度越大,稳定松弛阶段的松弛速率越大,应力松弛度越大;(3)循环气压下盐岩的应力松弛为循环性松弛,松弛曲线受控于其循环上下限对应的恒定气压时盐岩的应力松弛曲线;(4)松弛后盐岩的环境扫描电镜(environmental scanning electron microscopy,ESEM)图像表明,微裂纹产生和发展是造成盐岩内部损伤的主要机制。松弛后盐岩的细观结构损伤主要有晶粒碎屑、晶内裂纹、沿晶裂纹和穿晶裂纹;(5)改进的非线性二单元广义Maxwell松弛模型可以较好地描述不同的启动应力、气压条件下盐岩的应力松弛行为,为盐穴压缩空气储能库的稳定性评估提供一定参考。展开更多
针对持续扰动下的分布式状态耦合非线性系统,提出一种新的多耦合分布式经济模型预测控制(Economic model predictive control,EMPC)策略.由于耦合非线性系统的经济性能函数的非凸性和非正定性,首先引入关于经济最优平衡点的正定辅助函...针对持续扰动下的分布式状态耦合非线性系统,提出一种新的多耦合分布式经济模型预测控制(Economic model predictive control,EMPC)策略.由于耦合非线性系统的经济性能函数的非凸性和非正定性,首先引入关于经济最优平衡点的正定辅助函数和相应的辅助优化问题.接着,利用辅助函数的最优值函数构造原始分布式EMPC的一类隐式收缩约束.然后,建立状态耦合分布式EMPC的递推可行性和闭环系统关于最优经济平衡点的输入到状态稳定性(Input-to-state stability,ISS).最后,以耦合的四个连续搅拌釜反应器(Continuous stirred tank reactors,CSTRs)为例,验证本文所提策略的有效性.展开更多
基金Project(2007CB714202) supported by the National Key Basic Research Program of ChinaProject(SLDRCE10-B-07) supported by theMinistry of Science and Technology of China
文摘An element coupling model (ECM) method was proposed to simulate the global behavior and local damage of a structure.In order to reflect the local damage and improve the computational efficiency,three-dimensional (3D) solid elements and one-dimensional (1D) beam element were coupled by the multi-point constraint equations.A reduced scale 1?8 model test was simulated by the ECM and a full three dimensional model (3DM) contrastively.The results show that the global behavior and local damages of ECM agree well with the test and 3DM.It is indicated that the proposed method can be used in the structural nonlinear analysis accurately and efficiently.
基金Project(51375001) supported by the National Natural Science Foundation of ChinaProject(2013CB035400) supported by the National Basic Research Program of China
文摘When the tunneling boring machine(TBM) cutterhead tunnels, the excessive vibration and damage are a severe engineering problem, thereby the anti-vibration design is a key technology in the disc cutter system. The structure of disc cutter contains many joint interfaces among cutter ring, cutter body, bearings and cutter shaft. On account of the coupling for dynamic contact and the transfer path among joint interface, mechanical behavior of disc cutter becomes extremely complex under the impact of heavy-duty, which puts forward higher requirements for disc cutter design. A multi-degree-of-freedom coupling dynamic model, which contains a cutter ring, a cutter body, two bearings and cutter shaft, is established, considering the external stochastic excitations, bearing nonlinear contact force, multidirectional mutual coupling vibration, etc. Based on the parameters of an actual project and the strong impact external excitations, the modal properties and dynamic responses are analyzed, as well as the cutter shaft and bearings' loads and load transmission law are obtained. Numerical results indicate the maximum radial and axial cutter ring amplitudes of dynamic responses are 0.568 mm and 0.112 mm; the maximum radial and axial vibration velocities are 41.1 mm/s and 38.9 mm/s; the maximum radial and axial vibration accelerations are 94.7 m/s2 and 58.6 m/s2; the maximum swing angle and angular velocity of cutter ring are 0.007° and 0.0074 rad/s, respectively. Finally, the maximum load of bearing roller is 40.3 k N. The proposed research lays a foundation for structure optimization design of disc cutter and cutter base, as well as model selection, modification and fatigue life of the cutter bearing.
基金Project(2015AA043003)supported by National High-technology Research and Development Program of ChinaProject(GY2016ZB0068)supported by Application Technology Research and Development Program of Heilongjiang Province,ChinaProject(SKLR201301A03)supported by Self-planned Task of State Key Laboratory of Robotics and System(Harbin Institute of Technology),China
文摘In order to improve the trajectory tracking precision and reduce the synchronization error of a 6-DOF lightweight robot, nonlinear proportion-deviation （N-PD） cross-coupling synchronization control strategy based on adjacent coupling error analysis is presented. The mathematical models of the robot, including kinematic model, dynamic model and spline trajectory planing, are established and verified. Since it is difficult to describe the real-time contour error of the robot for complex trajectory, the adjacent coupling error is analyzed to solve the problem. Combined with nonlinear control and coupling performance of the robot, N-PD cross-coupling synchronization controller is designed and validated by simulation analysis. A servo control experimental system which mainly consists of laser tracking system, the robot mechanical system and EtherCAT based servo control system is constructed. The synchronization error is significantly decreased and the maximum trajectory error is reduced from 0.33 mm to 0.1 mm. The effectiveness of the control algorithm is validated by the experimental results, thus the control strategy can improve the robot＇s trajectory tracking precision significantly.
基金Projects(50574091, 50774084) supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions+1 种基金Project(CXLX12_0949) supported by Research and Innovation Project for College Graduates of Jiangsu Province, ChinaProject(2013DXS03) supported by the Fundamental Research Funds for the Central Universities, China
文摘A model of vibrating device coupling two pendulums (VDP) which is highly nonlinear was put forward to conduct vibration analysis. Based on energy analysis, dynamic equations with cubic nonlinearities were established using Lagrange's equation. In order to obtain approximate solution, multiple time scales method, one of perturbation technique, was applied. Cases of non-resonant and 1:1:2:2 internal resonant were discussed. In the non-resonant case, the validity of multiple time scales method is confirmed, comparing numerical results derived from fourth order Runge-Kutta method with analytical results derived from first order approximate expression. In the 1:1:2:2 internal resonant case, modal amplitudes of Aa1 and Ab2 increase, respectively, from 0.38 to 0.63 and from 0.19 to 0.32, while the corresponding frequencies have an increase of almost 1.6 times with changes of initial conditions, indicating the existence of typical nonlinear phenomenon. In addition, the chaotic motion is found under this condition.
文摘A class of chaotic map called piecewise-quadratic-equation map to design feedback stream cipher is proposed. Such map can generate chaotic signals that have uniform distribution function, δ-like autocorrelation function. Compared with the piecewise-linear map, this map provides enhanced security in that they can maintain the original perfect statistical properties, as well as overcome the defect of piecewise-linearity and expand the key space. This paper presents a scheme to improve the local complexity of the chaotic stream cipher based on the piecewise-quadratic-equationmap. Both the theoretic analysis and the results of simulation show that this scheme improves the microstructure of the phase-space graph on condition that the good properties of the original scheme are remained.
文摘为保障国家能源安全,近年来国家加大了对压缩空气储能技术的研发投入,这类工程较以往常规工程情况更为复杂,岩石的应力松弛特性也会受更多因素影响。针对压缩空气储能工程特点,从新研究角度出发,进行了气压-应力耦合作用下盐岩应力松弛试验,探究不同气压、轴向启动应力条件下盐岩的应力松弛特性。结果表明:(1)盐岩的应力松弛宏观规律不受气压影响,气压-应力耦合作用下盐岩的应力松弛仍可划分为快速、减速、稳定松弛3个阶段。其中,快速松弛阶段的松弛量占整体松弛量50%左右,而稳定松弛阶段在整个松弛过程中占比最大;(2)盐岩应力松弛受轴向启动应力和气压影响,轴向启动应力和气压越高,应力松弛初速度越大,稳定松弛阶段的松弛速率越大,应力松弛度越大;(3)循环气压下盐岩的应力松弛为循环性松弛,松弛曲线受控于其循环上下限对应的恒定气压时盐岩的应力松弛曲线;(4)松弛后盐岩的环境扫描电镜(environmental scanning electron microscopy,ESEM)图像表明,微裂纹产生和发展是造成盐岩内部损伤的主要机制。松弛后盐岩的细观结构损伤主要有晶粒碎屑、晶内裂纹、沿晶裂纹和穿晶裂纹;(5)改进的非线性二单元广义Maxwell松弛模型可以较好地描述不同的启动应力、气压条件下盐岩的应力松弛行为,为盐穴压缩空气储能库的稳定性评估提供一定参考。
文摘针对持续扰动下的分布式状态耦合非线性系统,提出一种新的多耦合分布式经济模型预测控制(Economic model predictive control,EMPC)策略.由于耦合非线性系统的经济性能函数的非凸性和非正定性,首先引入关于经济最优平衡点的正定辅助函数和相应的辅助优化问题.接着,利用辅助函数的最优值函数构造原始分布式EMPC的一类隐式收缩约束.然后,建立状态耦合分布式EMPC的递推可行性和闭环系统关于最优经济平衡点的输入到状态稳定性(Input-to-state stability,ISS).最后,以耦合的四个连续搅拌釜反应器(Continuous stirred tank reactors,CSTRs)为例,验证本文所提策略的有效性.
