Attitude maneuver of liquid-filled spacecraft with an appendage as a cantilever beam by momentum wheel is studied. The dynamic equations are derived by conserva- tion of angular momentum and force equilibrium principl...Attitude maneuver of liquid-filled spacecraft with an appendage as a cantilever beam by momentum wheel is studied. The dynamic equations are derived by conserva- tion of angular momentum and force equilibrium principle. A feedback control strategy of the momentum wheel is ap- plied for the attitude maneuver. The residual nutation of the spacecraft in maneuver process changes with some chosen parameters, such as steady state time, locations of the liq- uid container and the appendage, and appendage parame- ters. The results indicate that locations in the second and fourth quadrants of the body-fixed coordinate system and the second quadrant of the wall of the main body are better choices for.placing the liquid containers and the appendage than other locations if they can be placed randomly. Higher density and thicker cross section are better for lowering the residual nutation if they can be changed. Light appendage can be modeled as a rigid body, which results in a larger residual nutation than a flexible model though. The resid- ual nutation decreases with increasing absolute value of the initial sloshing angular height.展开更多
This paper proposes an intelligent controller for motion control of robotic systems to obtain high precision tracking without the need for a real-time trial and error method.In addition, a new self-tuning algorithm ha...This paper proposes an intelligent controller for motion control of robotic systems to obtain high precision tracking without the need for a real-time trial and error method.In addition, a new self-tuning algorithm has been developed based on both the ant colony algorithm and a fuzzy system for real-time tuning of controller parameters. Simulations and experiments using a real robot have been addressed to demonstrate the success of the proposed controller and validate the theoretical analysis. Obtained results confirm that the proposed controller ensures robust performance in the presence of disturbances and parametric uncertainties without the need for adjustment of control law parameters by a trial and error method.展开更多
经典的哈希分级时间轮算法在管理大规模定时器时存在响应时间长、累积时延高等缺点。该文借鉴"高速缓存"思想,提出了一种时间轮改进算法(Cached And Timing Wheels,CTW),基于多线程和缓存机制,提前查找和存储即将超时的定时...经典的哈希分级时间轮算法在管理大规模定时器时存在响应时间长、累积时延高等缺点。该文借鉴"高速缓存"思想,提出了一种时间轮改进算法(Cached And Timing Wheels,CTW),基于多线程和缓存机制,提前查找和存储即将超时的定时器。该算法能够充分利用多核CPU的性能,优化开启、查找和停止定时器的操作,提升大规模定时器的管理效率。实践表明,CTW算法在管理大规模定时器时能够缩短响应时间,消除累积时延,提高定时器精度。展开更多
基金supported by the National Natural Science Foundation of China (11072030)
文摘Attitude maneuver of liquid-filled spacecraft with an appendage as a cantilever beam by momentum wheel is studied. The dynamic equations are derived by conserva- tion of angular momentum and force equilibrium principle. A feedback control strategy of the momentum wheel is ap- plied for the attitude maneuver. The residual nutation of the spacecraft in maneuver process changes with some chosen parameters, such as steady state time, locations of the liq- uid container and the appendage, and appendage parame- ters. The results indicate that locations in the second and fourth quadrants of the body-fixed coordinate system and the second quadrant of the wall of the main body are better choices for.placing the liquid containers and the appendage than other locations if they can be placed randomly. Higher density and thicker cross section are better for lowering the residual nutation if they can be changed. Light appendage can be modeled as a rigid body, which results in a larger residual nutation than a flexible model though. The resid- ual nutation decreases with increasing absolute value of the initial sloshing angular height.
文摘This paper proposes an intelligent controller for motion control of robotic systems to obtain high precision tracking without the need for a real-time trial and error method.In addition, a new self-tuning algorithm has been developed based on both the ant colony algorithm and a fuzzy system for real-time tuning of controller parameters. Simulations and experiments using a real robot have been addressed to demonstrate the success of the proposed controller and validate the theoretical analysis. Obtained results confirm that the proposed controller ensures robust performance in the presence of disturbances and parametric uncertainties without the need for adjustment of control law parameters by a trial and error method.
文摘经典的哈希分级时间轮算法在管理大规模定时器时存在响应时间长、累积时延高等缺点。该文借鉴"高速缓存"思想,提出了一种时间轮改进算法(Cached And Timing Wheels,CTW),基于多线程和缓存机制,提前查找和存储即将超时的定时器。该算法能够充分利用多核CPU的性能,优化开启、查找和停止定时器的操作,提升大规模定时器的管理效率。实践表明,CTW算法在管理大规模定时器时能够缩短响应时间,消除累积时延,提高定时器精度。
