云原生数据库具有开箱即用、弹性伸缩、按需付费等优势,是目前学术界和工业界的研究热点.当前,云原生数据库仅支持“一写多读”,即读写事务集中在单一的读写节点,只读事务分散到多个只读节点.将读写事务集中在单一的读写节点,制约了系...云原生数据库具有开箱即用、弹性伸缩、按需付费等优势,是目前学术界和工业界的研究热点.当前,云原生数据库仅支持“一写多读”,即读写事务集中在单一的读写节点,只读事务分散到多个只读节点.将读写事务集中在单一的读写节点,制约了系统的读写事务处理能力,难以满足读写密集型业务需求.为此,提出D3C(deterministic concurrency control cloud-native database)架构,通过设计基于确定性并发控制的云原生数据库事务处理机制来突破一写多读的限制,支持多个读写节点并发执行读写事务.D3C将事务分拆为子事务,并根据预先确定的全局顺序在各节点独立执行这些子事务,以满足多个读写节点上事务执行的可串行化.此外,提出基于多版本机制的异步批量数据持久化等机制以保证事务处理的性能,并提出基于一致性点的故障恢复机制以实现高可用.实验结果表明,D3C在满足云原生数据库关键需求的同时,在写密集场景下能够达到一写多读性能的5.1倍.展开更多
A nonlinear robust controller was presented to improve the tracking control performance of a flexible air-breathing hypersonic vehicle(AHV) which is subjected to system parametric uncertainties and unknown additive ti...A nonlinear robust controller was presented to improve the tracking control performance of a flexible air-breathing hypersonic vehicle(AHV) which is subjected to system parametric uncertainties and unknown additive time-varying disturbances.The longitudinal dynamic model for the flexible AHV was used for the control development.High-gain observers were designed to compensate for the system uncertainties and additive disturbances.Small gain theorem and Lyapunov based stability analysis were utilized to prove the stability of the closed loop system.Locally uniformly ultimately bounded tracking of the vehicle's velocity,altitude and attack angle were achieved under aeroelastic effects,system parametric uncertainties and unknown additive disturbances.Matlab/Simulink simulation results were provided to validate the robustness of the proposed control design.The simulation results demonstrate that the tracking errors stay in a small region around zero.展开更多
The path following problem for an underactuated unmanned surface vehicle(USV) in the Serret-Frenet frame is addressed. The control system takes account of the uncertain influence induced by model perturbation, externa...The path following problem for an underactuated unmanned surface vehicle(USV) in the Serret-Frenet frame is addressed. The control system takes account of the uncertain influence induced by model perturbation, external disturbance, etc. By introducing the Serret-Frenet frame and global coordinate transformation, the control problem of underactuated system(a nonlinear system with single-input and ternate-output) is transformed into the control problem of actuated system(a single-input and single-output nonlinear system), which simplifies the controller design. A backstepping adaptive sliding mode controller(BADSMC)is proposed based on backstepping design technique, adaptive method and theory of dynamic slide model control(DSMC). Then, it is proven that the state of closed loop system is globally stabilized to the desired configuration with the proposed controller. Simulation results are presented to illustrate the effectiveness of the proposed controller.展开更多
To explore the precise dynamic response of the levitation system with active controller, a maglev guide way-electromagnet-air spring-cabin coupled model is derived firstly. Based on the mathematical model, it shows th...To explore the precise dynamic response of the levitation system with active controller, a maglev guide way-electromagnet-air spring-cabin coupled model is derived firstly. Based on the mathematical model, it shows that the inherent nonlinearity, inner coupling, misalignments between the sensors and actuators, load uncertainties and external disturbances are the main issues that should be solved in engineering. Under the assumptions that the loads and external disturbance are measurable, the backstepping module controller developed in this work can tackle the above problems effectively. In reality, the load is uncertain due to the additions of luggage and passengers, which will degrade the dynamic performance. A load estimation algorithm is introduced to track the actual load asymptotically and eliminate its influence by tuning the parameters of controller online. Furthermore,considering the external disturbances generated by crosswind, pulling motor and air springs, the extended state observer is employed to estimate and suppress the external disturbance. Finally, results of numerical simulations illustrating closed-loop performance are provided.展开更多
文摘云原生数据库具有开箱即用、弹性伸缩、按需付费等优势,是目前学术界和工业界的研究热点.当前,云原生数据库仅支持“一写多读”,即读写事务集中在单一的读写节点,只读事务分散到多个只读节点.将读写事务集中在单一的读写节点,制约了系统的读写事务处理能力,难以满足读写密集型业务需求.为此,提出D3C(deterministic concurrency control cloud-native database)架构,通过设计基于确定性并发控制的云原生数据库事务处理机制来突破一写多读的限制,支持多个读写节点并发执行读写事务.D3C将事务分拆为子事务,并根据预先确定的全局顺序在各节点独立执行这些子事务,以满足多个读写节点上事务执行的可串行化.此外,提出基于多版本机制的异步批量数据持久化等机制以保证事务处理的性能,并提出基于一致性点的故障恢复机制以实现高可用.实验结果表明,D3C在满足云原生数据库关键需求的同时,在写密集场景下能够达到一写多读性能的5.1倍.
基金Supported by National Natural Science Foundation of P. R. China （60325311, 60534010, 60572070, 60521003）, the Program for Changjiang Scholars and Innovative Research Team in University （IRT0421）
文摘柔韧的 H 联网了控制方法因为有无常和时间的模糊系统推迟的 Takagi-Sugeno (T-S ) 被介绍。一个州的反馈控制器经由联网的控制系统(NCS ) 被设计理论。为有 H 性能的柔韧的稳定性的足够的状况被获得。在网络传播和包退学学生的导致网络的延期被分析。模拟结果显示出这个控制计划的有效性。
基金Projects(90916004,60804004)supported by the National Natural Science Foundation of ChinaProject supported by the Program for the New Century,ChinaProject(NCET-09-0590)supported by Excellent Talents in University,China
文摘A nonlinear robust controller was presented to improve the tracking control performance of a flexible air-breathing hypersonic vehicle(AHV) which is subjected to system parametric uncertainties and unknown additive time-varying disturbances.The longitudinal dynamic model for the flexible AHV was used for the control development.High-gain observers were designed to compensate for the system uncertainties and additive disturbances.Small gain theorem and Lyapunov based stability analysis were utilized to prove the stability of the closed loop system.Locally uniformly ultimately bounded tracking of the vehicle's velocity,altitude and attack angle were achieved under aeroelastic effects,system parametric uncertainties and unknown additive disturbances.Matlab/Simulink simulation results were provided to validate the robustness of the proposed control design.The simulation results demonstrate that the tracking errors stay in a small region around zero.
基金Project(51409061)supported by the National Natural Science Foundation of ChinaProject(2013M540271)supported by China Postdoctoral Science Foundation+1 种基金Project(LBH-Z13055)supported by Heilongjiang Postdoctoral Financial Assistance,ChinaProject(HEUCFD1403)supported by Basic Research Foundation of Central Universities,China
文摘The path following problem for an underactuated unmanned surface vehicle(USV) in the Serret-Frenet frame is addressed. The control system takes account of the uncertain influence induced by model perturbation, external disturbance, etc. By introducing the Serret-Frenet frame and global coordinate transformation, the control problem of underactuated system(a nonlinear system with single-input and ternate-output) is transformed into the control problem of actuated system(a single-input and single-output nonlinear system), which simplifies the controller design. A backstepping adaptive sliding mode controller(BADSMC)is proposed based on backstepping design technique, adaptive method and theory of dynamic slide model control(DSMC). Then, it is proven that the state of closed loop system is globally stabilized to the desired configuration with the proposed controller. Simulation results are presented to illustrate the effectiveness of the proposed controller.
基金Projects(60404003,11202230)supported by the National Natural Science Foundation of China
文摘To explore the precise dynamic response of the levitation system with active controller, a maglev guide way-electromagnet-air spring-cabin coupled model is derived firstly. Based on the mathematical model, it shows that the inherent nonlinearity, inner coupling, misalignments between the sensors and actuators, load uncertainties and external disturbances are the main issues that should be solved in engineering. Under the assumptions that the loads and external disturbance are measurable, the backstepping module controller developed in this work can tackle the above problems effectively. In reality, the load is uncertain due to the additions of luggage and passengers, which will degrade the dynamic performance. A load estimation algorithm is introduced to track the actual load asymptotically and eliminate its influence by tuning the parameters of controller online. Furthermore,considering the external disturbances generated by crosswind, pulling motor and air springs, the extended state observer is employed to estimate and suppress the external disturbance. Finally, results of numerical simulations illustrating closed-loop performance are provided.
