Control and Stability of the Multi-Robots System

Executive control under stress: Relation to reappraisal ability and depressive symptoms

In the present research, we examined why some people have more difficulty than others in staying faithful to their romantic partners. Three studies supported our main prediction that executive control is associated with romantically involved individuals' ability to stay faithful. Study 1 showed that participants with a higher level of executive control reported less difficulty in staying faithful to their partners than did those with lower levels of executive control. In Study 2, romantically involved male participants were placed in a waiting room together with an attractive female confederate. Results showed that participants with a higher level of executive control showed less flirting behavior with the confederate than did those with lower levels of executive control. Study 3 demonstrated that a higher level of executive control was related to a lower expressed desire to meet an attractive other, but only for romantically involved participants. Together, these studies showed that executive control helps romantically involved individuals to deal with the lure of attractive alternatives.

Introduction. The article is devoted to the analysis of the stability of the electric power system (EPS) in mountainous areas using the Hurwitz criterion. In mountainous regions, the EPS faces a number of specific problems, such as complex terrain, remoteness of consumers and an increased probability of power transmission line failures. An important task is to develop a mathematical model that takes these features into account and to conduct an analysis of the stability of the system using the Hurwitz criterion. The purpose of the research: stability analysis of the system “high-pressure hydroelectric power plant – electric power system” using the Hurwitz criterion; identification of critical parameters of the system that affect its stability, and application of various optimization methods to improve the reliability and safety of the EPS in mountainous regions. Objects and methods. The object of the study is the high-pressure hydroelectric power plant (HPP) of PJSC RusHydro – Zaramagskaya HPP. The following methods were used for stability analysis: numerical modeling (integration of differential equations); state variable method; Laplace method; frequency response method; analytical methods for finding an exact solution to differential equations. Results and discussions. The results of the study demonstrate that the Gurwitz criterion is an effective tool for analyzing the stability of complex electric power systems, especially in mountainous areas. In the work, this method was successfully applied to analyze the static stability of the system taking into account automatic excitation control. Conclusion. A mathematical model has been developed that takes into account the specific conditions of mountainous areas. An analysis of the static stability of the system has been conducted taking into account the automatic excitation control (AEC). Critical parameters that affect the stability of the system, such as the load angle and the AEC gain factors, have been identified. It has been shown that increasing the accuracy of voltage maintenance can lead to a violation of stability in high-load modes. A method has been proposed for determining the minimum permissible gain factor, which allows avoiding aperiodic instability. Prospects for further research. In the future, possible alternative methods of stability analysis should be considered, such as frequency methods or methods based on Lyapunov theory, which could complement the results obtained using the Hurwitz criterion. A more detailed dynamic stability analysis should also be presented, which could provide a more complete understanding of the system’s behavior in transient conditions.

According to the interaction between the inverter and the grid in the large-scale photovoltaic grid-connected system, an auxiliary system based on grid connection of a single inverter is introduced. Research shows that the stability of the inverter output current in large-scale photovoltaic grid-connected systems depends on the stability of the auxiliary system and the stability of the inverter itself. But the stability of the total grid-connected current depends only on the stability of the auxiliary system. Therefore, a method for stability analysis of large-scale photovoltaic grid-connected systems is proposed. For a large-scale photovoltaic grid-connected system that is connected to the ideal grid through the grid impedance Zg after the inverters of the same specification and model are connected in parallel, the stable determination conditions are: (1) The inverter itself is stable, that is, a single inverter is stable when it is directly connected to the ideal power grid; (2) A single inverter in a large-scale PV grid-connected system is stable through the grid impedance nZg to the ideal grid. The stability analysis method can transform the research on the stability of large-scale photovoltaic grid-connected systems into the stability of the grid-connected system of a single inverter. For the multi-inverter parallel grid-connected system with uniform specifications and models, the stability analysis method is applicable regardless of whether all inverter current loop input reference currents are identical. The simulation results verify the correctness of the theoretical analysis.

In this reply to the comment of McVay and Kane (2010)Watkins’s (2008) elaborated control theory informs their perspective on the role of executive control in mind wandering. I argue that although in a number of places the elaborated control theory is consistent with the perspective of McVay and Kane that mind wandering represents a failure of executive control, their account makes a number of claims that are not articulated in the elaborated control theory—most notably, the hypothesis that level of construal moderates entry of thoughts into awareness. Moreover, the relevant literature suggests that the relationship between level of construal and executive control may be more complex, and may be determined by multiple factors beyond those proposed in this executive-control failure account of mind wandering. Finally, the implications of this model of mind wandering for understanding repetitive thought in general are considered, and it is proposed that examining level of executive control as a further moderating variable within elaborated control theory may be of value.

Decentralized leader-following formation control of nonholonomic mobile robots by local measurement: A small-gain approach

The recent trend in the design of a robot system towards to increase the capibility of a single robot for the increasing demand in different applications at home, industry or military(Murry 2007). However, it greatly increases not only the unit production cost but also the design complexity. One of the best solution for this problem is certainly identified as using many of the low cost robots in terms of the cooperative manner. Accordingly, the formation system may constitute a more effective achievement than a single robot in regard to the union of the different functions in the different Wheeled Mobile Robots(WMRs) of a team such that the cooperative system tends to the better signal resolution and the higher performance of the information system etc. Sometimes we could also suffer the task which is very diffcult to be achieved with a single robot, i.e., move a large size object from one place to another one or deal with the highly flexible tasks. The Multi-Robot Formation System (MRFS) is generally defined as a system contains a collection of the robotic subsystems which is able to be cooperation/competition with each other. The interconnected structure of the MRFS represents the physical or nonphysical interconnected relationship between any robots based on the specific robot in the formation team. Usually, the interconnected structure of the MRFS can be regarded as a topological structure with the communication system(Fax and Murray 2004; Olfati-Saber and Murray 2004). In other words, the topological structure is the foundation of the information system of the MRFS that is used to exchange their state information for the centralized coordinator(Matinez, Cortes et al. 2007). From geometrical persepective, the topological structure governs the shape stability or equivalently the graph rigidity(Lin, Francis et al. 2005) of the MRFS. Reviewing with the information aspect, the interconnected structure is naturally constructed with respect to the physical limitation of the sensors or the communication power of the WMRs, i.e., the resolution of the range sensor or the communication range etc. Sometimes, the interconnected structure may be assigned autonomously by the task manager who receives the global information of the systems and manages the performance of the task. The MRFS could surely be explained through the hierarchical system, ref. (Singh 1977). We emphasize that the MRFS is topologically constructed by the two hierarchy with low(subsystem) and high(interconnected system) level in this research. In most of the 15

This paper investigates the small-signal stability of power electronics-based power systems in frequency domain. A comparison between the impedance-based and the eigenvalue-based stability analysis methods is presented. A relation between the characteristics equation of the eigenvalues and poles and zeros of the minor-loop gain from the impedance-based analysis have been derived analytically. It is shown that both stability analysis methods can effectively determine the stability of the system. In the case of the impedance-based method, a low phase-margin in the Nyquist plot of the minor-loop gain indicates that the system can exhibit harmonic oscillations. A weakness of the impedance method is the limited observability of certain states given its dependence on the definition of local source-load subsystems, which makes it necessary to investigate the stability at different subsystems. To address this limitation, the paper discusses critical locations where the application of the method can reveal the impact of a passive component or a controller gain on the stability. On the other hand, the eigenvalue-based method, being global, can determine the stability of the entire system; however, it cannot unambiguously predict sustained harmonic oscillations in voltage source converter (VSC) based high voltage dc (HVdc) systems caused by pulse-width modulation (PWM) switching. To generalize the observations, the two methods have been applied to dc-dc converters. To illustrate the difference and the relation between the two-methods, the two stability analysis methods are then applied to a two-terminal VSC-based HVdc system as an example of power electronics-based power systems, and the theoretical analysis has been further validated by simulation and experiments.

In recent years, the proportion of new energy power generation in the power supply has increased yearly. However, the random volatility generated by new energy generation poses a new challenge to the stability of the power system. In terms of stability analysis, the traditional methods based on the deterministic system can not fully describe the influence of random fluctuation. In this case, this paper introduces the power grid stability analysis method considering random influence. Based on the original model, this paper introduces the random fluctuation simulated by the Gaussian process, establishes the power grid model described by nonlinear stochastic differential equations, and gives the numerical solution format of the model with the help of the Euler method. Secondly, compared with the traditional method of quantifying the size of the escaping state of the system, this method considers the influence of the random variable on the stability of the system at the same time. Therefore, this paper establishes the stability analysis system of the power grid and further considers the influence of power grid topology and system parameters on system stability. By analyzing the Brass paradox, it is found that it is more reasonable to quantify the stability of the system with exit time. Finally, this paper uses the stability analysis system to study the stability of the high voltage power grid in Shandong Province and gives suggestions to improve the stability.

Mirror Movements are Linked to Executive Control in Healthy and Brain-injured Adults

Attention deficit/hyperactivity disorder (ADHD) in children has been associated with attentional and executive problems, but also with socioemotional difficulties possibly associated with deficits in Theory of Mind (ToM). Socioemotional problems in ADHD are associated with more negative prognoses, notably interpersonal, educational problems, and an increased risk of developing other psychiatric disorders that emphasize the need to clarify the nature of their ToM deficits. In this study, we hypothesized that ToM dysfunction in children with ADHD is largely attributable to their attentional and/or executive deficits. Thirty-one children with ADHD (8–12 years, IQ > 85) and 31 typically developing (TD) children were assessed using executive functions (inhibition, planning, and flexibility) and attentional tasks, as well as two advanced ToM tasks (Reading the Mind in the Eyes and Faux Pas) involving different levels of executive control. Children with ADHD performed more poorly than TD children in attentional, executive function, and ToM tasks. Linear regression analyses conducted in the ADHD group indicated that inhibition scores predicted performance on the “Faux Pas” task the best, while attention scores were the best for predicting performance on the Reading the Mind in the Eyes task. When controlled for inhibition and attentional variables, ToM performance in children with ADHD was actually similar to TD children. Contrarily, controlling for ToM scores did not normalize performance for inhibition and attentional tasks in children with ADHD. This unidirectional relationship suggests that deficits in the EF and attentional domains are responsible for ToM deficits in ADHD, which therefore may contribute to their socioemotional difficulties.

Attentional and action control are two levels of executive control that are essential to early reading development. Together these levels enable the construction and monitoring of cognitive representations and of efficient task-behavior, which are both necessary to benefit from reading instruction. The longitudinal and unique contributions of this internal and external level of executive control to early reading are still unclear. We therefore examined how these control capacities facilitate reading development from kindergarten to second-grade. Attentional and action control and multiple early reading skills were assessed at all three time points. Structural Equation Modeling showed a mediation effect for attentional control and an indirect effect for action control to subsequent reading skills via the contributions to the precursor of phonological awareness. From these results it can be concluded that both types uniquely allowed for the emergence of kindergarten preliteracy skills, which in turn provided children with a better starting point for reading development in first- and second-grade.

Modeling and sensitivity analyses of VSP based virtual inertia controller in HVDC links of interconnected power systems

During the past few years, microgrids (MGs) have been becoming more attractive as effective means to integrate different distributed energy resources (DERs). To coordinate active and reactive power sharing among DERs, conventional droop control method is widely used as a decentralized control scheme. However, sharing powers among the sources based on the units' rated capacities is not an optimal solution in terms of economy and efficiency. In this paper, a new adaptive droop-based control strategy is proposed for AC MGs to optimally share MG load between corresponding units. The mentioned control strategy is developed in two levels. The upper control level is a mixed-objective optimization algorithm that provides optimal set-points for power generations considering system's constraints and goals, while the lower control level is responsible for tracking the reference signals coming from the upper level. To demonstrate the effectiveness of the proposed control strategy under different operating scenarios, simulation results in a benchmark MG are also presented.

An analytical framework for knowledge-based tuning of servo controllers