Azwirman Gusrialdi

Voronoi based coverage control with anisotropic sensors

In this paper the coverage control problem for mobile sensor networks is studied. The novelty is to consider an anisotropic sensor model where the performance of the sensor depends not only on the distance but also on the orientation to the target. By adapting the Lloyd algorithm and assuming a fixed and equal sensor orientation, a distributed control law is derived. Aside from coverage, the control law also guarantees collision avoidance between the agents. A simulation is provided to illustrate the results obtained in this paper. Furthermore, a numerical performance analysis to compare the anisotropic sensors modelling to isotropic approximations is performed.

Coverage control for mobile networks with limited-range anisotropic sensors

In this paper the coverage control for mobile sensor networks is studied. The novelty is to consider an anisotropic sensor model where the performance of the sensor depends not only on the distance but also on the orientation from the sensor to the target. Moreover we consider sensors with limited-range sensing defined by a probabilistic model and we assume that each robot is equipped with omni-directional communication capability. A gradient-based distributed algorithm is designed to maximize the joint detection probabilities of the events in the region of interest by the sensors. Simulations illustrate the results.

Performance-oriented communication topology design for large-scale interconnected systems

Communication networks provide a larger flexibility with respect to the control design of large-scale interconnected systems by allowing the information exchange between the local controllers of the subsystems. This paper introduces an approach for the design of the communication topology for the distributed control of large-scale interconnected systems in order to optimize the whole systems performance. First, a decentralized control law that stabilizes the overall interconnected systems is designed. Then the performance is improved by designing the distributed control law, i.e., allowing the controller of the subsystems to exchange information. As a novelty in this paper, the design of the communication topology between the controllers is considered. The problem is formulated as a mixed-integer optimization problem. Furthermore, it is shown that for a certain class of systems, the optimization problem can be reformulated resulting in a more explicit solution. In addition, it is shown that the proposed strategy also guarantees the stability of the whole system under the permanent communication links failure. The results are validated through simulations.

Coverage Control with Information Decay in Dynamic Environments

Abstract In this paper a method for coverage control for a convex region D ⊂ ℝ 2 in a dynamic environment is studied. An information map is introduced in which the information about each point is decaying with respect to time s.t. the robots must revisit them periodically. Also a time-varying density function is used for modeling moving points of interest. The considered gradient based control approach causes the cost function to stay within the desired bounds. But due to the non-stationary problem setup caused by the information decay it does not converge to a single point but to a bounded set, such that the robots keep gathering information continuously. With this method it is possible to gather information about several points of interest within the region D with only a few robots. In the end simulation results are presented to outline the effectiveness of the proposed control law.

Modeling inter-human movement coordination: synchronization governs joint task dynamics

Human interaction partners tend to synchronize their movements during repetitive actions such as walking. Research of inter-human coordination in purely rhythmic action tasks reveals that the observed patterns of interaction are dominated by synchronization effects. Initiated by our finding that human dyads synchronize their arm movements even in a goal-directed action task, we present a step-wise approach to a model of inter-human movement coordination. In an experiment, the hand trajectories of ten human dyads are recorded. Governed by a dynamical process of phase synchronization, the participants establish in-phase as well as anti-phase relations. The emerging relations are successfully reproduced by the attractor dynamics of coupled phase oscillators inspired by the Kuramoto model. Three different methods on transforming the motion trajectories into instantaneous phases are investigated and their influence on the model fit to the experimental data is evaluated. System identification technique allows us to estimate the model parameters, which are the coupling strength and the frequency detuning among the dyad. The stability properties of the identified model match the relations observed in the experimental data. In short, our model predicts the dynamics of inter-human movement coordination. It can directly be implemented to enrich human–robot interaction.

Study on the Effect of Time Delay on the Performance of Distributed Power Grids with Networked Cooperative Control

Abstract Future Distributed Power Grid (DPG) control systems may strongly benefit from the introduction of a communication network enabling cooperation between distributed generators. However, this typically comes at the cost that network induced time delay deteriorates control performance and possibly destabilizes the overall system. In this paper we study the effect of the time delay on the performance of a DPG with networked cooperative controllers exchanging state information of generators via a communication network and analyze up to which time delay such a communication network is still beneficial for the overall control performance. Here the delay is assumed to be constant and identical for all links. Standard Linear Quadratic Regulators (LQR) are designed together with communication topology, but without explicitly considering the time delay. We compare the Linear Quadratic (LQ) cost in infinite horizon as a measure of the performance of two cases: the networked cooperative controller with global information and time delay vs. the controller with only local information. It is observed that there exists a performance guaranteed time delay bound where the cost with the cooperative controller is smaller than without information exchange, i.e. it is still beneficial to introduce a communication network. By means of a Linear Matrix Inequality (LMI) problem based on first order Pade approximation for time delay this performance guaranteed time delay bound is approximated in a systematic way. A numerical example is given to illustrate the result.

Scheduling and cooperative control of electric vehicles' charging at highway service stations

Due to their limited ranges, electric vehicles (EVs) need to be periodically charged during their long-distance travels on a highway. Compared to the fossil-fuel powered vehicles, the charging of a single EV takes much more time (up to 30 mins versus 2 mins). As the number of EVs on highways increases, adequate charging infrastructure needs to be put in place. Nonetheless waiting times for EVs to get charged at service stations could still vary significantly unless an appropriate scheduling coordination is in place and individual EVs make correct decisions about their choice of charging locations. This paper attempts to address both the system-level scheduling problem and the individual control problem, while requiring only distributed information about EVs and their charging at service stations along a highway. Specifically, we first develop a higher-level distributed scheduling algorithm to optimize the operation of the overall charging network. The scheduling algorithm uses only local information of traffic flows measured at the neighboring service stations (nodes), and it aims at adjusting the percentage of the EVs to be charged at individual stations so that all the charging resources along the highway are well (uniformly) utilized and the total waiting time is minimized. Then, a lower level cooperative control law is designed for individual EVs to decide whether or not it should charge its battery when approaching a specific service station by meeting the published scheduling level while taking into account its own battery constraint. Analytical designs are presented and their performance improvement is illustrated using simulation.

Joint Controller-Communication Topology Design for Distributed Wide-Area Damping Control of Power Systems

Abstract The recent development and deployment of the synchronized phasor measurement units (PMU) is allowing the wide-area monitoring and control of large-scale power systems. Furthermore, the integration of more communication technologies into the power system is giving an additional degree of freedom to the control design that may improve the performance of the overall system. Small-signal stability is an important requirement for power systems with the increasing number of distributed generation units. The oscillation modes of the power system have to be well damped in order to avoid contingencies such as blackouts. Wide-area controllers based on the real-time PMU measurements operating in centralized, distributed and decentralized manner have been widely proposed to damp the low-frequency oscillation of the large-scale interconnected power system. It has been shown that the damping performance can be improved by using the synchronized PMU data transmitted in real-time via communication network. However, only a few of the proposed methods take the structural constraint of the measurement data transmission into account. In this paper, we propose a method to design a distributed wide-area damping controller together with the communication topology in order to improve the damping performance of the power system. As a design strategy, first a decentralized controller that stabilizes the overall system is designed. Then, the damping performance is improved by designing the distributed control law, i.e. allowing the local controllers to exchange information. The problem is formulated as a mixed-integer optimization. Finally the proposed approach is evaluated in a five machine power system via a numerical simulation.

Robust design of cooperative systems against attacks

While the use of a communication network facilitates the development of cooperative control for networked systems, it comes at a price that the systems become vulnerable to data attacks by an adversary. In this paper, we consider consensus dynamics on networked systems with strongly connected directed graphs in the presence of an additive stealthy attacker. The attacker has a linear dynamics and can corrupt the local state feedback of the systems agents by interconnecting with their communication network and inserting external attacks (or injections) with the intent of destabilizing the consensus dynamics. In order to make the consensus dynamics robust against such attacks, a hidden network, interconnected with the original consensus network, is introduced. The hidden network is designed to maintain stability of the overall system by competitively interacting with the original consensus network but without requiring any information about the adversary. Lyapunov analysis and design methods are presented which provide an explicit rule on how to interconnect both networks. Furthermore, using the same analysis and design framework we show that the nodes that are being attacked can also be identified in a distributed manner. An example, which includes several scenarios, is used to illustrate the results.

Distributed deployment algorithms for robotic visual sensor networks in non-convex environment

This paper considers the deployment problem for mobile visual sensor networks equipped with omni-directional communication capability in a non-convex environment. The performance of the visual sensor is assumed to depend not only on the distance but also on the orientation from the sensor to the target. A gradient-based distributed deployment algorithms is designed to maximize the joint detection probabilities of the events in the region of interest by the sensors which introduces discontinuities caused by the obstacles. In addition, a potential function based algorithm is incorporated in order to guarantee the collision avoidance during the deployment of the sensors. The results are validated through numerical simulations.