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Bifurcation behavior and coexisting motions in a time-delayed power system

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Chinese Physics B 2015年第3期24卷 78-86页

作者：马美玲闵富红 school of electrical and automation engineering

With the increase of system scale, time delays have become unavoidable in nonlinear power systems, which add the complexity of system dynamics and induce chaotic oscillation and even voltage collapse events. In this paper, coexisting phenomenon in a fourth-order time-delayed power system is investigated for the first time with different initial *** the mechanical power, generator damping factor, exciter gain, and time delay varying, the specific characteristic of the time-delayed system, including a discontinuous ＂jump＂ bifurcation behavior is analyzed by bifurcation diagrams, phase portraits, Poincar′e maps, and power spectrums. Moreover, the coexistence of two different periodic orbits and chaotic attractors with periodic orbits are observed in the power system, respectively. The production condition and existent domain of the coexistence phenomenon are helpful to avoid undesirable behavior in time-delayed power systems.

关键词： chaotic oscillation time delays bifurcation diagrams coexisting motions

State and Output Feedback Finite-time Guaranteed Cost Control of Linear It Stochastic Systems

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Journal of Systems Science & Complexity 2015年第4期28卷 813-829页

作者： YAN Zhiguo ZHANG Guoshan WANG Jiankui ZHANG Weihai school of electrical engineering and automation Qilu University of Technology school of electrical engineering and automation Tianjin University College of electrical engineering and automation Shandong University of Science and Technology

The problem of guaranteed cost control based on finite-time stability for stochastic system is first investigated in this *** motivation of solving this problem arises from an observation that finite/infinite-horizon guaranteed cost control does not consider the transient performance of the closed-loop system,but guaranteed cost control based on finite-time stability involves this practical *** order to explain this problem explicitly,a concept of the stochastic finite-time guaranteed cost control is introduced,and then some new sufficient conditions for the existence of state and output feedback finite-time guaranteed cost controllers are derived,which guarantee finite-time stochastic stability of closed-loop systems and an upper bound of a quadratic cost ***,this problem is reduced to a convex optimization problem with matrix inequality constraints and a new solving algorithm is ***,an example is given to illustrate the effectiveness of the proposed method.

关键词： Finite-time stability guaranteed cost control matrix inequalities stochastic systems.

Analytical solutions of transient pulsed eddy current problem due to elliptical electromagnetic concentrative coils

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Chinese Physics B 2010年第12期19卷 30-42页

作者：肖春燕张军 Department of electrical engineering School of Automation and Electrical EngineeringBeihang University

The electromagnetic concentrative coils are indispensable in the functional magnetic stimulation and have potential applications in nondestructive testing. In this paper, we propose a figure-8-shaped coil being composed of two arbitrary oblique elliptical coils, which can change the electromagnetic concentrative region and the magnitude of eddy current density by changing the elliptical shape and/or spread angle between two elliptical coils. Pulsed current is usually the excitation source in the functional magnetic stimulation, so in this paper we derive the analytical solutions of transient pulsed eddy current field in the time domain due to the elliptical concentrative coil placed in an arbitrary position over a half-infinite plane conductor by making use of the scale-transformation, the Laplace transform and the Fourier transform are used in our derivation. Calculation results of field distributions produced by the figure-8-shaped elliptical coil show some behaviours as follows： 1） the eddy currents are focused on the conductor under the geometric symmetric centre of figure-8-shaped coil; 2） the greater the scale factor of ellipse is, the higher the eddy current density is and the wider the concentrative area of eddy current along y axis is; 3） the maximum magnitude of eddy current density increases with the increase of spread angle. When spread angle is 180°, there are two additional reverse concentrative areas on both sides of x axis.

关键词： transient pulsed eddy current analytical solution elliptical electromagnetic concentra-tive coil functional magnetic stimulation

Intelligent monitoring-based safety system of massage robot

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Journal of Central South University 2016年第10期23卷 2647-2658页

作者：胡宁李长胜王利峰胡磊徐晓军邹雲鹏胡玥沈晨 school of automation Science and electrical engineering Beihang University school of Mechanical engineering and automation Beihang University school of Mechanical and electrical engineering Harbin Engineering University

As an important attribute of robots, safety is involved in each link of the full life cycle of robots, including the design, manufacturing, operation and maintenance. The present study on robot safety is a systematic project. Traditionally, robot safety is defined as follows: robots should not collide with humans, or robots should not harm humans when they collide. Based on this definition of robot safety, researchers have proposed ex ante and ex post safety standards and safety strategies and used the risk index and risk level as the evaluation indexes for safety methods. A massage robot realizes its massage therapy function through applying a rhythmic force on the massage object. Therefore, the traditional definition of safety, safety strategies, and safety realization methods cannot satisfy the function and safety requirements of massage robots. Based on the descriptions of the environment of massage robots and the tasks of massage robots, the present study analyzes the safety requirements of massage robots; analyzes the potential safety dangers of massage robots using the fault tree tool; proposes an error monitoring-based intelligent safety system for massage robots through monitoring and evaluating potential safety danger states, as well as decision making based on potential safety danger states; and verifies the feasibility of the intelligent safety system through an experiment.

关键词： robot fault tree safety strategies for robots intelligent safety

Complex network analysis in inclined oil-water two-phase flow

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Chinese Physics B 2009年第12期18卷 5249-5258页

作者：高忠科金宁德 school of electrical engineering and automation Tianjin University

Complex networks have established themselves in recent years as being particularly suitable and flexible for representing and modelling many complex natural and artificial systems. Oil-water two-phase flow is one of the most complex systems. In this paper, we use complex networks to study the inclined oil water two-phase flow. Two different complex network construction methods are proposed to build two types of networks, i.e. the flow pattern complex network （FPCN） and fluid dynamic complex network （FDCN）. Through detecting the community structure of FPCN by the community-detection algorithm based on K-means clustering, useful and interesting results are found which can be used for identifying three inclined oil-water flow patterns. To investigate the dynamic characteristics of the inclined oil-water two-phase flow, we construct 48 FDCNs under different flow conditions, and find that the power-law exponent and the network information entropy, which are sensitive to the flow pattern transition, can both characterize the nonlinear dynamics of the inclined oil-water two-phase flow. In this paper, from a new perspective, we not only introduce a complex network theory into the study of the oil-water two-phase flow but also indicate that the complex network may be a powerful tool for exploring nonlinear time series in practice.

关键词： two-phase flow complex networks community structure nonlinear dynamics

Adaptive synchronization control of coupled chaotic neurons in an external electrical stimulation

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Chinese Physics B 2013年第5期22卷 620-625页

作者：于海涛王江邓斌魏熙乐陈颖源 school of electrical engineering and automation Tianjin University

In this paper we present a combined algorithm for the synchronization control of two gap junction coupled chaotic FitzHugh-Nagumo （FHN） neurons in an external electrical stimulation. The controller consists of a combination of dynam- ical sliding mode control and adaptive backstepping control. The combined algorithm yields an adaptive dynamical sliding mode control law which has the advantage over static sliding mode-based controllers of being chattering-free, i.e., a suffi- ciently smooth control input signal is generated. It is shown that the proposed control scheme can not only compensate for the system uncertainty, but also guarantee the stability of the synchronized error system. In addition, numerical simulations are also performed to demonstrate the effectiveness of the proposed adaptive controller.

关键词： FitzHugh-Nagumo neuron synchronization adaptive control

Bursting synchronization in clustered neuronal networks

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Chinese Physics B 2013年第1期22卷 556-562页

作者：于海涛王江邓斌魏熙乐 school of electrical engineering and automation Tianjin University

Neuronal networks in the brain exhibit the modular （clustered） property, i.e., they are composed of certain subnetworks with differential internal and external connectivity. We investigate bursting synchronization in a clustered neuronal network. A transition to mutual-phase synchronization takes place on the bursting time scale of coupled neurons, while on the spiking time scale, they behave asynchronously. This synchronization transition can be induced by the variations of inter- and intra coupling strengths, as well as the probability of random links between different subnetworks. Considering that some pathological conditions are related with the synchronization of bursting neurons in the brain, we analyze the control of bursting synchronization by using a time-periodic external signal in the clustered neuronal network, Simulation results show a frequency locking tongue in the driving parameter plane, where bursting synchronization is maintained, even in the presence of external driving. Hence, effective synchronization suppression can be realized with the driving parameters outside the frequency locking region.

关键词： bursting synchronization neuronal network cluster external signal

Design and analysis of bidirectional driven float-type wave power generation system

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Journal of Modern Power Systems and Clean Energy 2018年第1期6卷 50-60页

作者： Hongwei FANG Yue TAO Shuai ZHANG Zhaoxia XIAO school of electrical engineering and automation Tianjin University school of electrical engineering and automation Tianjin Polytechnic University

The dynamic model for a bidirectional driven float-type wave power generation system design is presented in this *** gravity,buoyancy and drag force acting on the wave energy converter(WEC)are all *** analytical expression of the torque applied on the rotor is given based on a linear model of the switched reluctance generator(SRG).The SRG usually rotates with low velocity in the WEC *** this situation,current chopping control(CCC)is adopted with fixed turn-on angle and turn-off angle control mode to have a quick response for ***,in order to make the float keep in phase with the wave so as to improve the power generation efficiency,the reference current is dynamically adjusted according to the wave motion at all working *** maximum power point tracking(MPPT)of system is achieved.A simulation model is developed in MATLAB for the bidirectional driven float-type wave power generation system with real wave statistical characteristics taken into *** results show that the WEC can output desired torque periodically with high efficiency and good ***,the feasibility of applying a SRG in a WEC is also verified.

关键词： Wave energy converter Force analysis Current chopping control Dynamical reference current setting Maximum power point tracking

Self-sustained firing activities of the cortical network with plastic rules in weak AC electrical fields

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Chinese Physics B 2012年第7期21卷 604-610页

作者：秦迎梅王江门聪赵佳魏熙乐邓斌 school of electrical engineering and automation Tianjin University

Both external and endogenous electrical fields widely exist in the environment of cortical neurons. The effects of a weak alternating current （AC） field on a neural network model with synaptic plasticity are studied. It is found that self-sustained rhythmic firing patterns, which are closely correlated with the cognitive functions, are significantly modified due to the self-organizing of the network in the weak AC field. The activities of the neural networks are affected by the synaptic connection strength, the exterrtal stimuli, and so on. In the presence of learning rules, the synaptic connections can be modulated by the external stimuli, which will further enhance the sensitivity of the network to the external signal. The properties of the external AC stimuli can serve as control parameters in modulating the evolution of the neural network.

关键词： spike-timing-dependent plasticity (STDP) weak electrical field rhythmic activity