The velocity feedback in a load simulator with a motor synchronizing in position is achieved by installing a tachometer generator between tile shaft and shell of the loading motor, and thes not only decreases the dist...The velocity feedback in a load simulator with a motor synchronizing in position is achieved by installing a tachometer generator between tile shaft and shell of the loading motor, and thes not only decreases the disturbance torque of tile load simlilator greatly but also improves its dynamic performance.展开更多
In data stream management systems (DSMSs), how to maintain the quality of queries is a difficult problem because both the processing cost and data arrival rates are highly unpredictable. When the system is overloaded,...In data stream management systems (DSMSs), how to maintain the quality of queries is a difficult problem because both the processing cost and data arrival rates are highly unpredictable. When the system is overloaded, quality degrades significantly and thus load shedding becomes necessary. Unlike processing overloading in the general way which is only by a feedback control (FB) loop to obtain a good and stable performance over data streams, a feedback plus feed-forward control (FFC) strategy is introduced in DSMSs, which have a good quality of service (QoS) in the aspects of miss ratio and processing delay. In this paper, a quality adaptation framework is proposed, in which the control-theory-based techniques are leveraged to adjust the application behavior with the considerations of the current system status. Compared to previous solutions, the FFC strategy achieves a good quality with a waste of fewer resources.展开更多
The paper proposes a novel H∞ load frequency control(LFC) design method for multi-area power systems based on an integral-based non-fragile distributed fixed-order dynamic output feedback(DOF) tracking-regulator cont...The paper proposes a novel H∞ load frequency control(LFC) design method for multi-area power systems based on an integral-based non-fragile distributed fixed-order dynamic output feedback(DOF) tracking-regulator control scheme. To this end, we consider a nonlinear interconnected model for multiarea power systems which also include uncertainties and timevarying communication delays. The design procedure is formulated using semi-definite programming and linear matrix inequality(LMI) method. The solution of the proposed LMIs returns necessary parameters for the tracking controllers such that the impact of model uncertainty and load disturbances are minimized. The proposed controllers are capable of receiving all or part of subsystems information, whereas the outputs of each controller are local. These controllers are designed such that the resilient stability of the overall closed-loop system is guaranteed. Simulation results are provided to verify the effectiveness of the proposed scheme. Simulation results quantify that the distributed(and decentralized) controlled system behaves well in presence of large parameter perturbations and random disturbances on the power system.展开更多
Due to the nonlinearity of the reactor power system, the load tracking situation is closely related to the initial steady-state power and the final steady-state power after the introduction of the state feedback contr...Due to the nonlinearity of the reactor power system, the load tracking situation is closely related to the initial steady-state power and the final steady-state power after the introduction of the state feedback controller. Therefore, when the initial power and the final stable power are determined, the particle swarm optimization algorithm is used to find the optimal controller parameters to minimize the load tracking error. Since there are many combinations of initial stable power and final stable power, it is not possible to find the optimal controller parameters for all combinations, so the neural network is used to take the final stable power and the initial stable power as input, and the optimal controller parameters as the output. This method obtains the optimal state feedback controller switching control method can achieve a very excellent load tracking effect in the case of continuous power change, in the power change time point, the response is fast, in the controller parameter switching time point, the actual power does not fluctuate due to the change of controller parameters. .展开更多
The optimal control is investigated for linear systems affected by external harmonic disturbance and applied to vibration control systems of offshore steel jacket platforms. The wave-induced force is the dominant load...The optimal control is investigated for linear systems affected by external harmonic disturbance and applied to vibration control systems of offshore steel jacket platforms. The wave-induced force is the dominant load that offshore structures are subjected to, and it can be taken as harmonic excitation for the system. The linearized Morison equation is employed to estimate the wave loading. The main result concerns the existence and design of a realizable optimal regulator, which is proposed to damp the forced oscillation in an optimal fashion. For demonstration of the effectiveness of the control scheme, the platform performance is investigated for different wave states. The simulations are based on the tuned mass damper and the active mass damper control devices. It is demonstrated that the control scheme is useful in reducing the displacement response of jacket-type offshore platforms.展开更多
A system which consists of a loading chamber unit, displacement sensor, data collector and processor, and a feedback control, was established for applying mechanical forces to single plant cells. The method works by c...A system which consists of a loading chamber unit, displacement sensor, data collector and processor, and a feedback control, was established for applying mechanical forces to single plant cells. The method works by compressing an agar cell-suspension block between parallel surfaces through using a force-feedback control circuit coupled to a microchip, delivering the pre-defined. The actual controlled stimulus is achieved whilst measuring the force being imposed on the cell, and its deformation. TheArabidopsisprotoplasts were utilized to test the system. It provides an experimental approach to investigate the mechanoresponses of plant cellsin vitroconditions.展开更多
在含非线性负载的光伏并网系统中,光伏发电单元、非线性负载、电网三者之间的相互作用可能导致系统出现振荡,因此提出一种改进的电容电流反馈有源阻尼(capacitor current feedback active damping, CCFAD)控制方法。首先,采用谐波线性...在含非线性负载的光伏并网系统中,光伏发电单元、非线性负载、电网三者之间的相互作用可能导致系统出现振荡,因此提出一种改进的电容电流反馈有源阻尼(capacitor current feedback active damping, CCFAD)控制方法。首先,采用谐波线性化方法建立含非线性负载的光伏并网系统序阻抗模型,并基于阻抗模型和对数频率稳定判据揭示含非线性负载的光伏并网系统振荡特性。随后,基于负电阻理论定义阻抗相对灵敏度指标,评价不同参数变化对系统阻抗特性的影响程度,获取影响系统稳定性的关键参数。基于不同参数的阻抗相对灵敏度分析,提出一种改进的CCFAD方法。该方法拓展了传统CCFAD的正阻尼区域,有效地改善了系统输出阻抗的相位裕度,提高了系统稳定性。最后,在Matlab/Simulink中搭建仿真模型,验证了分析方法的正确性和所提控制策略的有效性。展开更多
文摘The velocity feedback in a load simulator with a motor synchronizing in position is achieved by installing a tachometer generator between tile shaft and shell of the loading motor, and thes not only decreases the disturbance torque of tile load simlilator greatly but also improves its dynamic performance.
基金Supported by the National Key R&D Program of China(2016YFC1401900)the National Science Foundation of China(61173029,61672144)
文摘In data stream management systems (DSMSs), how to maintain the quality of queries is a difficult problem because both the processing cost and data arrival rates are highly unpredictable. When the system is overloaded, quality degrades significantly and thus load shedding becomes necessary. Unlike processing overloading in the general way which is only by a feedback control (FB) loop to obtain a good and stable performance over data streams, a feedback plus feed-forward control (FFC) strategy is introduced in DSMSs, which have a good quality of service (QoS) in the aspects of miss ratio and processing delay. In this paper, a quality adaptation framework is proposed, in which the control-theory-based techniques are leveraged to adjust the application behavior with the considerations of the current system status. Compared to previous solutions, the FFC strategy achieves a good quality with a waste of fewer resources.
文摘The paper proposes a novel H∞ load frequency control(LFC) design method for multi-area power systems based on an integral-based non-fragile distributed fixed-order dynamic output feedback(DOF) tracking-regulator control scheme. To this end, we consider a nonlinear interconnected model for multiarea power systems which also include uncertainties and timevarying communication delays. The design procedure is formulated using semi-definite programming and linear matrix inequality(LMI) method. The solution of the proposed LMIs returns necessary parameters for the tracking controllers such that the impact of model uncertainty and load disturbances are minimized. The proposed controllers are capable of receiving all or part of subsystems information, whereas the outputs of each controller are local. These controllers are designed such that the resilient stability of the overall closed-loop system is guaranteed. Simulation results are provided to verify the effectiveness of the proposed scheme. Simulation results quantify that the distributed(and decentralized) controlled system behaves well in presence of large parameter perturbations and random disturbances on the power system.
文摘Due to the nonlinearity of the reactor power system, the load tracking situation is closely related to the initial steady-state power and the final steady-state power after the introduction of the state feedback controller. Therefore, when the initial power and the final stable power are determined, the particle swarm optimization algorithm is used to find the optimal controller parameters to minimize the load tracking error. Since there are many combinations of initial stable power and final stable power, it is not possible to find the optimal controller parameters for all combinations, so the neural network is used to take the final stable power and the initial stable power as input, and the optimal controller parameters as the output. This method obtains the optimal state feedback controller switching control method can achieve a very excellent load tracking effect in the case of continuous power change, in the power change time point, the response is fast, in the controller parameter switching time point, the actual power does not fluctuate due to the change of controller parameters. .
文摘The optimal control is investigated for linear systems affected by external harmonic disturbance and applied to vibration control systems of offshore steel jacket platforms. The wave-induced force is the dominant load that offshore structures are subjected to, and it can be taken as harmonic excitation for the system. The linearized Morison equation is employed to estimate the wave loading. The main result concerns the existence and design of a realizable optimal regulator, which is proposed to damp the forced oscillation in an optimal fashion. For demonstration of the effectiveness of the control scheme, the platform performance is investigated for different wave states. The simulations are based on the tuned mass damper and the active mass damper control devices. It is demonstrated that the control scheme is useful in reducing the displacement response of jacket-type offshore platforms.
文摘A system which consists of a loading chamber unit, displacement sensor, data collector and processor, and a feedback control, was established for applying mechanical forces to single plant cells. The method works by compressing an agar cell-suspension block between parallel surfaces through using a force-feedback control circuit coupled to a microchip, delivering the pre-defined. The actual controlled stimulus is achieved whilst measuring the force being imposed on the cell, and its deformation. TheArabidopsisprotoplasts were utilized to test the system. It provides an experimental approach to investigate the mechanoresponses of plant cellsin vitroconditions.
文摘在含非线性负载的光伏并网系统中,光伏发电单元、非线性负载、电网三者之间的相互作用可能导致系统出现振荡,因此提出一种改进的电容电流反馈有源阻尼(capacitor current feedback active damping, CCFAD)控制方法。首先,采用谐波线性化方法建立含非线性负载的光伏并网系统序阻抗模型,并基于阻抗模型和对数频率稳定判据揭示含非线性负载的光伏并网系统振荡特性。随后,基于负电阻理论定义阻抗相对灵敏度指标,评价不同参数变化对系统阻抗特性的影响程度,获取影响系统稳定性的关键参数。基于不同参数的阻抗相对灵敏度分析,提出一种改进的CCFAD方法。该方法拓展了传统CCFAD的正阻尼区域,有效地改善了系统输出阻抗的相位裕度,提高了系统稳定性。最后,在Matlab/Simulink中搭建仿真模型,验证了分析方法的正确性和所提控制策略的有效性。
