This paper derives a distance-based formation control method to maintain the desired formation shape for spacecraft in a gravitational potential field. The method is an analogy of a virtual spring-damper mesh. Spacecr...This paper derives a distance-based formation control method to maintain the desired formation shape for spacecraft in a gravitational potential field. The method is an analogy of a virtual spring-damper mesh. Spacecraft are connected virtually by spring-damper pairs. Convergence analysis is performed using the energy method. Approximate expressions for the distance errors and control accelerations at steady state are derived by using algebraic graph representations and results of graph rigidity. Analytical results indicate that if the underlying graph of the mesh is rigid, the convergence to a static shape is assured, and higher formation control precision can be achieved by increasing the elastic coefficient without increasing the control accelerations. A numerical example of spacecraft formation in low Earth orbit confirms the theoretical analysis and shows that the desired formation shape can be well achieved using the presented method, whereas the orientation of the formation can be kept pointing to the center of the Earth by the gravity gradient. The method is decentralized, and uses only relative measurement information. Constructing a distributed virtual structure in space can be the general application area. The proposed method can serve as an active shape control law for the spacecraft formations using propellantless internal forces.展开更多
In order to investigate the mechanism of the temperature oscillation in loop heat pipes,this paper investigated the movement of the phase interface as the changed input power by a mass-spring-damper model.The model wa...In order to investigate the mechanism of the temperature oscillation in loop heat pipes,this paper investigated the movement of the phase interface as the changed input power by a mass-spring-damper model.The model was solved with MATLAB and was used to explain the high-frequency and low-amplitude temperature oscillation.Temperature variation with the input power from 20 W to 75 W was investigated based on a LHP prototype in a literature.The model agreed well with the experimental data in the literature.The simulation results suggested that the movement of the liquid column was caused by the fluctuation of pressure difference applied on the liquid column and the stiffness coefficients of the vapor springs increasing with the input power.According to parameter analyses,the temperature oscillation at the outlet of the condenser can be weakened by increasing the mass of the liquid column and keeping the temperature at the outlet of the condenser steady.展开更多
An innovative variable stiffness device is proposed and investigated based on numerical simulations. The device, called a folding variable stiffness spring （FVSS）, can be widely used, especially in tuned mass dampe...An innovative variable stiffness device is proposed and investigated based on numerical simulations. The device, called a folding variable stiffness spring （FVSS）, can be widely used, especially in tuned mass dampers （TMDs） with adaptive stiffness. An important characteristic of FVSS is its capability to change the stiffness between lower and upper bounds through a small change of distance between its supports. This special feature results in lower time-lag errors and readjustment in shorter time intervals. The governing equations of the device are derived and simplified for a symmetrical FVSS with similar elements. This device is then used to control a single-degree-of-freedom （SDOF） structure as well as a multi-degree-of-freedom （MDOF） structure via a semi-active TMD. Numerical simulations are conducted to compare several control cases for these structures. To make it more realistic, a real direct current motor with its own limitations is simulated in addition to an ideal control case with no limitations and both the results are compared. It is shown that the proposed device can be effectively used to suppress undesirable vibrations of a structure and considerably improves the performance of the controller compared to a passive device.展开更多
对隧道、桥梁结构和沿线建筑而言,浮置板减振性能优异,但其对轨道板及其上部结构的耗能能力有限。针对此问题,将调谐质量粒子阻尼技术应用于轨道交通振动控制领域,提出一种基于调谐质量粒子阻尼器(Tuned Mass Particle Damper,TMPD)的...对隧道、桥梁结构和沿线建筑而言,浮置板减振性能优异,但其对轨道板及其上部结构的耗能能力有限。针对此问题,将调谐质量粒子阻尼技术应用于轨道交通振动控制领域,提出一种基于调谐质量粒子阻尼器(Tuned Mass Particle Damper,TMPD)的耗能型钢弹簧浮置板结构。基于调谐质量阻尼器(Tuned Mass Damper,TMD)及粒子阻尼理论,利用1:1浮置板轨道进行室内试验,通过落轴试验研究调谐质量粒子阻尼器安装前后钢弹簧浮置板轨道动力学特性。研究结果表明:TMPD能显著降低浮置板轨道在固有频率11.7 Hz附近的振动响应,浮置板加速度分频振级损失最大可达11.9 dB;安装TMPD的耗能型钢弹簧浮置板轨道从钢轨到地面的振动衰减最大可达23.6 dB,表明其具有优异的隔振效果;进行Z振级评价分析可得,耗能型钢弹簧浮置板Z振级约降低5 dB,在保证隔振效率基础上,调谐质量粒子阻尼器可提高浮置板轨道的耗能能力。展开更多
基金supported by the National Natural Science Foundation of China (Nos. 61273351 and 61673390)
文摘This paper derives a distance-based formation control method to maintain the desired formation shape for spacecraft in a gravitational potential field. The method is an analogy of a virtual spring-damper mesh. Spacecraft are connected virtually by spring-damper pairs. Convergence analysis is performed using the energy method. Approximate expressions for the distance errors and control accelerations at steady state are derived by using algebraic graph representations and results of graph rigidity. Analytical results indicate that if the underlying graph of the mesh is rigid, the convergence to a static shape is assured, and higher formation control precision can be achieved by increasing the elastic coefficient without increasing the control accelerations. A numerical example of spacecraft formation in low Earth orbit confirms the theoretical analysis and shows that the desired formation shape can be well achieved using the presented method, whereas the orientation of the formation can be kept pointing to the center of the Earth by the gravity gradient. The method is decentralized, and uses only relative measurement information. Constructing a distributed virtual structure in space can be the general application area. The proposed method can serve as an active shape control law for the spacecraft formations using propellantless internal forces.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51276012)
文摘In order to investigate the mechanism of the temperature oscillation in loop heat pipes,this paper investigated the movement of the phase interface as the changed input power by a mass-spring-damper model.The model was solved with MATLAB and was used to explain the high-frequency and low-amplitude temperature oscillation.Temperature variation with the input power from 20 W to 75 W was investigated based on a LHP prototype in a literature.The model agreed well with the experimental data in the literature.The simulation results suggested that the movement of the liquid column was caused by the fluctuation of pressure difference applied on the liquid column and the stiffness coefficients of the vapor springs increasing with the input power.According to parameter analyses,the temperature oscillation at the outlet of the condenser can be weakened by increasing the mass of the liquid column and keeping the temperature at the outlet of the condenser steady.
文摘An innovative variable stiffness device is proposed and investigated based on numerical simulations. The device, called a folding variable stiffness spring （FVSS）, can be widely used, especially in tuned mass dampers （TMDs） with adaptive stiffness. An important characteristic of FVSS is its capability to change the stiffness between lower and upper bounds through a small change of distance between its supports. This special feature results in lower time-lag errors and readjustment in shorter time intervals. The governing equations of the device are derived and simplified for a symmetrical FVSS with similar elements. This device is then used to control a single-degree-of-freedom （SDOF） structure as well as a multi-degree-of-freedom （MDOF） structure via a semi-active TMD. Numerical simulations are conducted to compare several control cases for these structures. To make it more realistic, a real direct current motor with its own limitations is simulated in addition to an ideal control case with no limitations and both the results are compared. It is shown that the proposed device can be effectively used to suppress undesirable vibrations of a structure and considerably improves the performance of the controller compared to a passive device.
文摘对隧道、桥梁结构和沿线建筑而言,浮置板减振性能优异,但其对轨道板及其上部结构的耗能能力有限。针对此问题,将调谐质量粒子阻尼技术应用于轨道交通振动控制领域,提出一种基于调谐质量粒子阻尼器(Tuned Mass Particle Damper,TMPD)的耗能型钢弹簧浮置板结构。基于调谐质量阻尼器(Tuned Mass Damper,TMD)及粒子阻尼理论,利用1:1浮置板轨道进行室内试验,通过落轴试验研究调谐质量粒子阻尼器安装前后钢弹簧浮置板轨道动力学特性。研究结果表明:TMPD能显著降低浮置板轨道在固有频率11.7 Hz附近的振动响应,浮置板加速度分频振级损失最大可达11.9 dB;安装TMPD的耗能型钢弹簧浮置板轨道从钢轨到地面的振动衰减最大可达23.6 dB,表明其具有优异的隔振效果;进行Z振级评价分析可得,耗能型钢弹簧浮置板Z振级约降低5 dB,在保证隔振效率基础上,调谐质量粒子阻尼器可提高浮置板轨道的耗能能力。
