Finite-time circle surrounding control for multi-agent systems

In this paper, a finite-time circle surrounding control problem for multi-agent systems is investigated. The objective is to make all the surrounding agents eventually distribute on a circle uniformly and all the target agents surrounded by this circle in the finite time. Both a distributed estimator and a distributed control protocol are presented to achieve such a goal. Firstly, an estimator of the targets’ geometric center is used to estimate the center of targets. Secondly, a distributed control protocol is proposed for each surrounding agent by using the value of the estimator to guarantee all the surrounding agents uniformly distribute on a circle and all the target agents are surrounded by this circle in the finite time. Then it is proved that the control goal can be achieved in the finite time. Finally, a simulation example is given to show the effectiveness of the proposed method.     

A bio-inspired pursuit strategy for optimal control with partially constrained final state

We discuss a biologically inspired cooperative control strategy which allows a group of autonomous systems to solve optimal control problems with free final time and partially constrained final state. The proposed strategy, termed “generalized sampled local pursuit” (GSLP), mimics the way in which ants optimize their foraging trails, and guides the group toward an optimal solution, starting from an initial feasible trajectory. Under GSLP, an optimal control problem is solved in many “short” segments, which are constructed by group members interacting locally with lower information, communication and storage requirements compared to when the problem is solved all at once. We include a series of simulations that illustrate our approach.     

Guaranteed strategies with memory for alternative pursuit

A pursuit game is called alternative if, at any state of the game, a pursuer can terminate it on any of two given target sets and the Boltz payoff function differs on these sets only in the terminal part. By assumption, the optimal universal feedback strategies of the pursuer are known for each fixed terminal alternative. Endeavoring to decrease its payoff via the choice of an alternative, the pursuer may compare guaranteed results (e.g., at the initial and current states) and apply one of two fixed-alternative strategies. If both players optimize the choice of their alternatives depending on the position, the state of the pursuit game can enter some neighborhood of a hypersurface with equivalent alternatives (in the sense of payoffs) and stay there for a finite period of time. In different formalizations, the solutions generated by an appropriate differential equation with discontinuous right-hand side (ideal solutions, limits of Euler polygonal lines, generalized solutions) lead to different outcomes. For certain states, they even increase the payoff in comparison with the pursuit strategy based on the preferable alternative chosen at the initial state (due to sliding mode occurrence). The author introduces a method of constructing pursuit strategies with memory and a finite number of admissible switchings for the target alternative. The proposed method allows estimating the guaranteed result of the pursuer by confining to the solution concept of the limits of Euler polygonal lines.     

A global observer for autonomous systems with bounded trajectories

The problem of global observer design for autonomous systems is investigated in this paper. A constructive approach is presented for the explicit design of global observers for completely observable systems whose solution trajectories are bounded from any initial condition. Since the bound of a solution trajectory depends on the initial condition and is therefore not known a priori, the idea of universal control is employed to tune the observer gains on‐line, achieving global asymptotic convergence of the proposed high‐gain observer. Copyright © 2007 John Wiley & Sons, Ltd.     

Semi-globally tracking control for uncertain non-affine self-restructuring systems with state constraints

It is still an open problem to achieve tracking control with state constraints if the initial states are out of the constrained region. This underlying problem becomes more challenging if the system suffers from modeling uncertainties and external disturbances. In this paper, we investigate such problem for a class of uncertain nonaffine self-restructuring systems subject to state constraints in the absence of any limitation on the initial values of states. In order to steer the original system states into the desired constraint region in finite time, certain auxiliary system is firstly constructed via introducing auxiliary variables. By resorting to some auxiliary nonlinear functions, the original system with state constraints is transformed into an unconstrained one in the sense that the constraint problem of the original system is equivalent to ensuring the stability of the transformed one. By following the backstepping design technique, an adaptive control scheme is developed that enables the states to enter into the constrained region for any initial point within any fixed time and then never violate it. All the closed loop signals are ensured to be semi-globally uniformly ultimately bounded. Finally, one numerical simulation example is presented to verify the theoretical analysis.     

Development of the visible light communication device for swarm using nonlinear synchronization

This paper describes development of a visible light 4 Pulse position modulation (4PPM) data communication device for underwater swarms using a nonlinear synchronizing system. SWARM—a group robot that uses intelligence as a group—do as ants and bees, is expected to be useful for marine resource exploration. Specifically, numerous SWARMs will be grouped to explore marine resources efficiently. An important difficulty is the change in electronic circuit characteristics because of high water pressure in the deep sea. Development of small and simple underwater SWARM communication devices must eliminate this problem without using large pressure-proof containers. As described herein, we considered nonlinear synchronizing systems as effective because they can be synchronized even if system time constants differ. Such systems resemble the glow mechanism used by fireflies. They have individuality, but they flash synchronously when in a group. We developed a visible light communication device using this nonlinear synchronization system based on the firefly concept. Test results confirmed that they are synchronized even if a time constant difference exists between them. Furthermore, we achieved 4PPM data communication using the nonlinear synchronization signal as a communication clock.     

Analysing the novice analyst: cognitive models in software engineering

Cognitive problem-solving by novice systems analysts during a requirements analysis task was investigated by protocol analysis. Protocols were collected from 13 subjects who analysed a scheduling problem. Reasoning, planning, conceptual modelling and information gathering behaviours were recorded and subject's solutions were evaluated for completeness and accuracy. The protocols showed an initial problem scoping phase followed by more detailed reasoning. Performance in analysis was not linked to any one factor although reasoning was correlated with success. Poor performance could be ascribed to failure to scope the problem, poor formation of a conceptual model of the problem domain, or insufficient testing of hypotheses. Good performance concorded with well-formed conceptual models and good reasoning/testing abilities. The implication of these results for structured systems development methods and Computer-Aided Software Engineering (CASE) tools are discussed.     

Finite‐Time Consensus Problem for Second‐Order Multi‐Agent Systems Under Switching Topologies

This paper investigates the finite‐time consensus problem for multi‐agent systems with second‐order individual dynamics under switching topologies. A distributed continuous‐time protocol is designed to guarantee finite‐time consensus for homogeneous agents without predetermined leaders, i.e., it ensures agents asymptotically converge to an average consensus within finite time, even if the interaction topology among them is time‐varying but stepwise jointly‐connected. In particular, it introduces a distributed continuous‐time protocol to reach consensus in finite time and reduce the chattering together. Finally, the simulation results are also given to validate the proposed approach.     

Control of incompletely controllable differential-difference systems with delay

A problem of control of linear autonomous differential-difference systems for violation of the condition of complete controllability and uncontrolled initial state is studied. A problem of system trajectory nullification and its delay there within any specified time period is posed. A new condition for solvability of this problem is proved and a constructive solution is proposed.     

Decentralized control of multi-agent systems for swarming with a given geometric pattern

This paper addresses a problem of cooperative formation control of a network of self-deployed autonomous agents. We propose a decentralized motion coordination control for the agents so that they collectively move in a desired geometric pattern from any initial position. There are no predefined leaders in the group and only local information is required for the control. The control algorithm is developed using the ideas of information consensus, and its effectiveness is illustrated via numerical simulations.     

Exact non-linear Bayesian parameter estimation for autonomous compliant motion

This paper presents theoretical and experimental results for the estimation of large position and orientation inaccuracies during force-controlled compliant motion. This is a significant improvement over previous results. The estimation is based on position, velocity and force measurements. For large position and orientation inaccuracies, the non-linear estimation problem is not satisfactorily solved by existing Kalman filters. Therefore, a new Bayesian estimator is derived. The filter is derived independently of our application and is valid for static systems (parameter estimation) with any kind of non-linear measurement equation subject to Gaussian measurement uncertainty and for a limited class of dynamic systems. Experimental results for the estimation of the inaccurately known positions and orientations of contacting objects during autonomous compliant motion are presented.     

Gathering asynchronous oblivious mobile robots in a ring

We consider the problem of gathering identical, memoryless, mobile robots in one node of an anonymous unoriented ring. Robots start from different nodes of the ring. They operate in Look–Compute–Move cycles and have to end up in the same node. In one cycle, a robot takes a snapshot of the current configuration (Look), makes a decision to stay idle or to move to one of its adjacent nodes (Compute), and in the latter case makes an instantaneous move to this neighbor (Move). Cycles are performed asynchronously for each robot. For an odd number of robots we prove that gathering is feasible if and only if the initial configuration is not periodic, and we provide a gathering algorithm for any such configuration. For an even number of robots we decide the feasibility of gathering except for one type of symmetric initial configurations, and provide gathering algorithms for initial configurations proved to be gatherable.     

Exponential finite-time couple-group consensus for agents in cooperative-competitive networks via pinning method

This paper investigates the exponential finite-time couple-group consensus problem for multi-agent systems via pinning control method. Considering the hybrid cooperative and competitive interactions among the agents, a new nonlinear distributed control protocol is proposed. Under the pinning control scheme, the criteria for guaranteeing the system with weakly connected communication topology achieve exponential couple-group consensus in finite time are obtained, and the pinning control strategies are presented as well. Furthermore, the results show that the settling time for the system to reach consensus is independent of the initial states of the agents. Finally, the correctness of our results is verified by some simulations.     

Ensuring termination by typability

A term terminates if all its reduction sequences are of finite length. We show four type systems that ensure termination of well-typed π-calculus processes. The systems are obtained by successive refinements of the types of the simply typed π-calculus. For all (but one of) the type systems we also present upper bounds to the number of steps well-typed processes take to terminate. The termination proofs use techniques from term rewriting systems. We show the usefulness of the type systems on some non-trivial examples: the encodings of primitive recursive functions, the protocol for encoding separate choice in terms of parallel composition, a symbol table implemented as a dynamic chain of cells.     

智能机器人的自适应自主Agents的建模

在问题求解期间及穿越动态的、不可预测的环境的过程中 ,真实世界的问题需要自适应的求解方法来‘裁剪’Agent的行为 ,并使其落入任务域 ,否则不完备的知识、不确定性、不确定的Agents及过程的存在、硬件失灵和不精确性都会引发不确定事件的发生。自适应自主Agents是一种存在于动态的、不可预测的环境中 ,并试图满足一系列随时间变化的目标或动机的系统 ,而且此类Agents在处理这些目标的过程中 ,能基于已有的经验改进其能力。自适应自主Agents为智能机器人实现这一目标提供了一种新的途径。主要讨论了智能机器人的自适应自主Agents的建模问题 ,并指出它的局限性和开问题     

Heterogeneous consensus of higher‐order multi‐agent systems with mismatched uncertainties using sliding mode control

A robust consensus controller is proposed for heterogeneous higher‐order nonlinear multi‐agent systems, when the agent dynamics are involved with mismatched uncertainties. A distributed consensus protocol based on a time‐varying nonhomogeneous finite‐time disturbance observer and sliding mode control is designed to realize the network consensus of higher‐order multi‐agent systems. The time‐varying finite‐time disturbance observer overcomes the problem of peaking value near the initial time caused by the constant gain one and is designed to estimate the uncertainties and to mitigate the effect of mismatched uncertainties during the sliding mode. To eliminate the chattering phenomenon and ensure finite‐time convergence to the sliding surface, the control law is designed by using the super twisting algorithm. Finally numerical simulations are given to illustrate the validity of the proposed method. Copyright © 2016 John Wiley & Sons, Ltd.     

Decentralized event‐triggered circle formation control for multiagent systems via synchronous periodic event detection

This paper investigates circle formation problem of multiagent systems over a kind of strongly connected and weight‐unbalanced directed graphs. To solve the concerned problem, decentralized periodic event‐triggered algorithms subject to or not to time delays are proposed, which have the advantages of decreasing the overall burden of the network in terms of finite communication and control input updates. In such algorithms, each agent independently evaluates whether the locally sampled information of itself should be broadcasted to or not to its neighbors. Furthermore, another advantage of our proposed algorithms is to automatically exclude Zeno behavior, which should be seriously considered in a variety of event‐based network systems. Sufficient conditions on circle formation control are derived under which the states of all agents can be ensured to converge to some desired equilibrium point. Simulation results are given to validate the effectiveness of the proposed methods.     

Reach a nonlinear consensus for MAS via doubly stochastic quadratic operators

This technical note addresses the new nonlinear protocol class of doubly stochastic quadratic operators (DSQOs) for coordination of consensus problem in multi-agent systems (MAS). We derive the conditions for ensuring that every agent reaches consensus on a desired rate of the group's decision where the group decision value in its agent's initial statuses varies. Besides that, we investigate a nonlinear protocol sub-class of extreme DSQO (EDSQO) to reach a consensus for MAS to a common value with nonlinear low-complexity rules and fast time convergence if the interactions for each agent are not selfish. In addition, to extend the results to reach a consensus and to avoid the selfish case we specify a general class of DSQO for reaching a consensus under any given case of initial states. The case that MAS reach a consensus by DSQO is if each member of the agent group has positive interactions of DSQO (PDSQO) with the others. The convergence of both EDSQO and PDSQO classes is found to be directed towards the centre point. Finally, experimental simulations are given to support the analysis from theoretical aspect.     

基于UPPAAL的WSNs数据收集协议的建模与分析

无线传感器网络(Wireless Sensor Networks,WSNs)广泛应用于各类数据收集系统,如居民区无线抄表(包括水表、电表和燃气表)系统。数据收集协议设计的正确性与合理性是影响网络正常运作的关键因素。针对数据收集协议的实时性需求,提出了基于UPPAAL实时模型检查器的WSNs数据收集协议的建模与分析方法。由于UPPAAL的输入模型相对于一般时间自动机模型而言较为复杂,因此首先对所选数据收集协议的通信行为建立一般时间自动机模型,之后再将其进一步转换为UPPAAL的输入模型。为了阐明该方法的有效性,选择了一个实际的无线抄表数据收集协议WM2RP作为例子进行建模,并利用UPPAAL分析其性质。分析结果显示,该协议能够满足一些与安全性及可靠性相关的性质。为了从多角度对协议进行分析,进一步建立了WM2RP协议的异常模型和能耗模型。