Protocol For Consensus Research Articles

Can we develop consensus on long-term follow-up and surveillance of primary shoulder arthroplasty? A study protocol using a real-time Delphi technique among expert clinicians in the UK

BackgroundShoulder arthroplasty incidence is projected to continue its exponential growth and the resultant burden of monitoring patients with shoulder arthroplasty implants creates significant pressure on orthopaedic services. Surveillance offers the...

Model-based event/self-triggered fixed-time consensus of nonlinear multi-agent systems

To address model-based event-triggered fixed-time consensus of nonlinear multi-agent systems with both fixed topology and switching topologies, a novel model-based event-triggered protocol is presented. In the proposed protocol, agents in multi-agent systems update controllers by utilizing estimated state values in the triggered intervals. And for reducing the burdens of bandwidth further, the model-based event-triggered protocol is extended to self-triggered protocol which does not need continuous communication in triggered intervals. It is proven that Zeno behavior is excluded. Our main contributions are giving a novel distributed model-based event-triggered protocol for fixed-time consensus and extending it into a self-triggered protocol. Finally, a couple of simulation examples are provided to verify the effectiveness of the proposed protocols.

A new distributed protocol for consensus of discrete-time systems

In this paper, a new distributed protocol is proposed to force consensus in a discrete-time network of scalar agents with an arbitrarily assignable convergence rate. Several simulations validate the performances and the improvements with respect to more standard protocols.

Locally solvable tasks and the limitations of valency arguments

An elegant strategy for proving impossibility results in distributed computing was introduced in the celebrated FLP consensus impossibility proof. This strategy is local in nature as at each stage, one configuration of a hypothetical protocol for consensus is considered, together with future valencies of possible extensions. This proof strategy has been used in numerous situations related to consensus, leading one to wonder why it has not been used in impossibility results of two other well-known tasks: set agreement and renaming. This paper provides an explanation of why impossibility proofs of these tasks have been of a global nature. It shows that a protocol can always solve such tasks locally, in the following sense. Given a configuration and all its future valencies, if a single successor configuration is selected, then the protocol can reveal all decisions in this branch of executions, satisfying the task specification. This result is shown for both set agreement and renaming, implying that there are no local impossibility proofs for these tasks.

MWPoW+: A Strong Consensus Protocol for Intra-Shard Consensus in Blockchain Sharding

Blockchain sharding splits a blockchain into several shards where consensus is reached at the shard level rather than over the entire blockchain. It improves transaction throughput and reduces the computational resources required of individual nodes. But a derivation of trustworthy consensus within a shard becomes an issue as the longest chain based mechanisms used in conventional blockchains can no longer be used. Instead, a vote-based consensus mechanism must be employed. However, existing vote-based Byzantine fault tolerance consensus protocols do not offer sufficient security guarantees for sharded blockchains. First, when used to support consensus where only one block is allowed at a time (binary consensus), these protocols are susceptible to progress-hindering attacks (i.e., unable to reach a consensus). Second, when used to support a stronger type of consensus where multiple concurrent blocks are allowed (strong consensus), their tolerance of adversary nodes is low. This article proposes a new consensus protocol to address all these issues. We call the new protocol MWPoW +, as its basic framework is based on the existing Multiple Winners Proof of Work (MWPoW) protocol but includes new mechanisms to address the issues mentioned previously. MWPoW+ is a vote-based protocol for strong consensus, asynchronous in consensus derivation but synchronous in communication. We prove that it can tolerate up to f < n /2 adversary nodes in a n-node system as if using a binary consensus protocol and does not suffer from progress-hindering attacks.

An Adaptive Distributed Protocol for Finite-Time Infimum or Supremum Dynamic Consensus

In this letter, the problem of distributively tracking the minimum infimum (or maximum supremum) of a set of time-varying signals in finite-time is addressed. More specifically, each agent has access to a local time-varying exogenous signal, and all the agents are required to follow the minimum infimum (or the maximum supremum) of these signals in a distributed fashion. No assumption is made on the network size nor on the bounds of the exogenous signal derivatives. An adaptive protocol is provided which can provably solve the above problem in finite-time for multi-agent systems with undirected connected network topologies. Numerical simulations are provided to corroborate the theoretical findings.

Observer-based quadratic boundedness leader-following control for multi-agent systems

This paper presents the design of an observer-based quadratic boundedness protocol for leader-following consensus in multi-agent systems. The problem under consideration is to force all the agents to follow the trajectories of a virtual leader in spite of bounded disturbances which implies that the leader-following consensus is reached in a positively invariant and attractive ellipsoid. Under the framework of control synthesis in multi-agent systems subject to bounded disturbances, linear matrix inequality-based sufficient conditions are obtained for the computation of the controller and observer gains. The effectiveness of the proposed approach is demonstrated through simulations in a fleet of unmanned aerial vehicles subject to wind turbulence which are shown to achieve formation control.

Cocreating a Harmonized Living Lab for Big Data-Driven Hybrid Persona Development: Protocol for Cocreating, Testing, and Seeking Consensus.

BackgroundLiving Labs are user-centered, open innovation ecosystems based on a systematic user cocreation approach, which integrates research and innovation processes in real-life communities and settings. The Horizon 2020 Project VITALISE (Virtual Health and Wellbeing Living Lab Infrastructure) unites 19 partners across 11 countries. The project aims to harmonize Living Lab procedures and enable effective and convenient transnational and virtual access to key European health and well-being research infrastructures, which are governed by Living Labs. The VITALISE consortium will conduct joint research activities in the fields included in the care pathway of patients: rehabilitation, transitional care, and everyday living environments for older adults. This protocol focuses on health and well-being research in everyday living environments.ObjectiveThe main aim of this study is to cocreate and test a harmonized research protocol for developing big data–driven hybrid persona, which are hypothetical user archetypes created to represent a user community. In addition, the use and applicability of innovative technologies will be investigated in the context of various everyday living and Living Lab environments.MethodsIn phase 1, surveys and structured interviews will be used to identify the most suitable Living Lab methods, tools, and instruments for health-related research among VITALISE project Living Labs (N=10). A series of web-based cocreation workshops and iterative cowriting processes will be applied to define the initial protocols. In phase 2, five small-scale case studies will be conducted to test the cocreated research protocols in various real-life everyday living settings and Living Lab infrastructures. In phase 3, a cross-case analysis grounded on semistructured interviews will be conducted to identify the challenges and benefits of using the proposed research protocols. Furthermore, a series of cocreation workshops and the consensus seeking Delphi study process will be conducted in parallel to cocreate and validate the acceptance of the defined harmonized research protocols among wider Living Lab communities.ResultsAs of September 30, 2021, project deliverables Ethics and safety manual and Living lab standard version 1 have been submitted to the European Commission review process. The study will be finished by March 2024.ConclusionsThe outcome of this research will lead to harmonized procedures and protocols in the context of big data–driven hybrid persona development among health and well-being Living Labs in Europe and beyond. Harmonized protocols enable Living Labs to exploit similar research protocols, devices, hardware, and software for interventions and complex data collection purposes. Economies of scale and improved use of resources will speed up and improve research quality and offer novel possibilities for open data sharing, multidisciplinary research, and comparative studies beyond current practices. Case studies will also provide novel insights for implementing innovative technologies in the context of everyday Living Lab research.International Registered Report Identifier (IRRID)DERR1-10.2196/34567

Global Consensus of Positive Edge System With Sector Input Nonlinearities

This paper investigates the positive edge consensus problems for undirected networks, where each edge is modeled by a continuous-time positive system with sector input nonlinearities. Based on a given nodal network, the corresponding edge network is presented, and some relationships between the given nodal network and its edge network are given. The observer-based protocol for non-negative consensus is proposed. Rigorous theoretical analysis which considers both the input nonlinearities and the positivity constraint is introduced to achieve a global consensus result. Simultaneous stabilization problems are constructed for edge-based non-negative consensus using the maximum and the minimum nonzero eigenvalues of the edge Laplacian matrix. Furthermore, the robustness of the positive edge consensus to parameter perturbation is illustrated. Sufficient non-negative consensus conditions related to the bounds of system matrices are given, and the non-negative edge consensus conditions for star nodal networks are also given only using the vertex number. Iterative linear matrix inequalities (LMIs)/LMI algorithm is presented to obtain the feedback matrix and the observer matrix. The given theoretical results are finally illustrated by some simulations.

Neural Network-Based Distributed Adaptive Pre-Assigned Finite-Time Consensus of Multiple TCP/AQM Networks

In this study, a class of finite-time consensus of multiple transmission control protocol/active queue management (TCP/AQM) networks is investigated on the basis of a design idea of multi-agent systems, and for the first time, to our knowledge, a novel congestion control concept with neural networks is proposed. First, the problem statement and design goal of the consensus of multiple TCP/AQM networks is given. Then, a pre-assigned finite-time function is introduced to ensure that the tracking error approaches a pre-defined area within finite time. Furthermore, by combining a barrier Lyapunov function and backstepping technique, a neural network-based distributed adaptive finite-time control protocol for the output consensus of multiple TCP/AQM networks is presented, which can effectively generate the desired controls and ensure that the convergent time of all errors has nothing to do with the initial condition and design parameters. In addition, all signals in the closed-loop system are bounded. Finally, an example is given to further illustrate the effectiveness of the theoretical finding presented.

Core competencies for public health medicine: protocol for an Italian inter-society Delphi consensus

Abstract Background Developing core competencies is crucial for the quality of educational curricula in Public Health Medicine (PHM). The postgraduate medical School of Public Health of the University of Pisa developed a core curriculum for PHM specialists (CCV0), adapted from the list of core competencies promoted by the Association of Schools in Public Health of the European Region (ASPHER). Objectives We will apply the Garavalia method, a three-round step-wise Delphi consensus, for adapting the CCV0 to the Italian context. Participants will be enrolled through purposive sampling among the members of the Italian Society of Hygiene, Public Health and Preventive Medicine, aiming at the best possible balance between geographical distribution and professional profiles (PHM residents, academics, and Public Health operators). A sample of representatives of other PHM-related Italian Societies will also be included. Results We will invite 139 participants through e-mail invitations. During round zero, we will collect additional suggested competencies through an open-ended question. We will analyze data qualitatively and integrate the most relevant suggestions with the CCV0, resulting in the CCV1. A subgroup of 64 experts (among PHM residents, academics, and representatives of the included Societies) will participate in the following rounds. The first round will use Likert scales to measure agreement on the appropriateness of the CCV1 competencies. Consensus and agreement will be computed using the RAND/UCLA criteria. The final round will reach out for consensus repeating the same ratings for competencies classified as uncertain, with the help of quali-quantitave summaries of the answers of the first round. The final document (CC2) will report competencies classified as consensus or uncertain, with the corresponding level of consent. Conclusions The CC2 will enable current courses to be assessed and inform the design of future educational programs for Italian PHM residents. Key messages The Delphi method ensures anonymity and a balanced involvement of all stakeholders –including medical residents- in the development of a core curriculum for Public Health Medicine specialists. A consensus on core competencies in Public Health Medicine will enable the evaluation of current training curricula and the development of future educational programs.

Distributed adaptive consensus protocol with decaying gains

SummaryThis article brings a distributed adaptive protocol for consensus and synchronization in multiagent systems on directed communication networks. Agents are modeled as general linear time‐invariant systems. The proposed protocol introduces a novel adaptation scheme allowing control coupling gains to decay to their reference values. This approach improves upon existing adaptive consensus protocols which may result in overly large or even unbounded coupling gains. The protocol design in this article does not rely on any centralized information; hence it is distributed. Nevertheless, the price to pay for this is the need to estimate those reference values. Convergence of the overall network dynamics is guaranteed for correctly estimated references; otherwise, the trajectory of the system is only uniformly ultimately bounded. Two estimation algorithms are proposed: one based on the interval‐halving method and the other based on a distributed estimation of Laplacian eigenvalues. Numerical simulations validate the proposed approach.

A Hybrid Thermodynamic Control Protocol for Semistability and Consensus of Network Systems With Intermittent Information

Network systems involve distributed decision making for coordination of networks of dynamic agents and address a broad area of applications in science and engineering. In this article, we develop a thermodynamically based framework for addressing consensus problems using a hybrid control protocol architecture with a dynamic communication topology wherein communication events are triggered via state-dependent resettings consistent with thermodynamic principles. The proposed hybrid controller architecture involves the exchange of intermittent state information between agents guaranteeing that the closed-loop dynamical network is semistable to an equipartitioned equilibrium representing a state of information consensus consistent with basic thermodynamic principles.

Core Rehabilitation Outcome Set for Single Sided Deafness (CROSSSD) study: protocol for an international consensus on outcome measures for single sided deafness interventions using a modified Delphi survey

BackgroundSingle-sided deafness (SSD) describes the presence of a unilateral severe to profound sensorineural hearing loss. SSD disrupts spatial hearing and understanding speech in background noise. It has functional, psychological and social consequences. Potential options for rehabilitation include hearing aids and auditory implants. Benefits and harms of these interventions are documented inconsistently in the literature, using a variety of outcomes ranging from tests of speech perception to quality of life questionnaires. It is therefore difficult to compare interventions when rehabilitating SSD. The Core Rehabilitation Outcome Set for Single Sided Deafness (CROSSSD) study is an international initiative that aims to develop a minimum set of core outcomes for use in future trials of SSD interventions.Methods/designThe CROSSSD study adopts an international two-round online modified Delphi survey followed by a stakeholder consensus meeting to identify a patient-centred core outcome domain set for SSD based on what is considered critical and important for assessing whether an intervention for SSD has worked.DiscussionThe resulting core outcome domain set will act as a minimum standard for reporting in future clinical trials and could have further applications in guiding the use of outcome measures in clinical practice. Standardisation will facilitate comparison of research findings.

Discrete-time event-triggered higher order sliding mode control for consensus of 2-DOF robotic arms

This paper proposes a discrete-time event-triggered higher-order sliding mode protocol for the leader-following consensus of Discrete Homogeneous Multi-Agent Systems (DHMAS). The discrete version of the Super-Twisting Algorithm (DSTA) which is one of the most popular algorithm of higher order sliding mode control blended with event-triggered control approach is used to design the protocol. The DSTA algorithm is robust against the uncertainties present in the DHMAS and improve the consensus performance. The event-triggered control approach reduces the usage of power and communication resources due to the intermittent communication with the neighboring agents to achieve consensus. For implementing the proposed consensus protocol, each follower agent of DHMAS monitor for the event-triggering condition as defined in this paper. The sufficient condition for global stability with proposed consensus protocol is also derived to ensure the stable operation of DHMAS. Further, the proposed protocol is implemented on a discrete homogeneous multi-agent system set up comprise of 2-DOF flexible joint robotic arm considering one robotic arm as a leader and others as followers to show the efficacy of the proposed protocol.

A hybrid protocol for the average consensus of multi-agent systems with impulse time window

In this paper, a control protocol is proposed, which can make the states of multi-agent systems achieve average consensus over time. Periodicity is one of the characteristics of the control protocol, we divide each period of the control protocol into three parts, some continuous inputs for part 1, an impulse input with time window for part 2, and another continuous inputs for part 3. The system is called A hybrid protocol for the average consensus of multi-agent systems with impulse time window. We study the control protocol by constructing the Lyapunov function and mathematical induction method. We give a strict mathematical proof of the feasibility of the control protocol. At the end of this paper, we use a numerical example to simulate the control protocol, and the experimental results are excellent. Due to impulse time window is considered in each control protocol, the control protocol in this paper is closer to reality and can be better applied to industrial production, which makes the control protocol more practical and efficient.

Optimal Consensus via Distributed Protocol for Second-Order Multiagent Systems

This article is devoted to the optimal protocol for the leader-following consensus of second-order multiagent systems. Remarkably, the global consensus cost functional and the directed topology are pregiven, and the optimal protocol to be sought is distributed. This makes the Riccati-based strategies inapplicable, by which merely centralized protocol can be derived. As the main contribution of this article, an effective strategy of seeking a distributed optimal protocol is proposed for second-order agents over the digraph of the directed tree. Detailedly, the feasibility of distributed optimal protocol is first affirmed, that is, the existence of optimal gain parameters can be guaranteed. Then, by recursively deriving the completely explicit formulas of the consensus errors of relative position and velocity, an online implementable algorithm is developed to achieve the parameterization of the cost functional, that is, to obtain the explicit formula of the cost functional with respect to gain parameters of all agents. Lastly, the desired optimal gain parameters are obtained by minimizing the explicit formula.

Event-triggered Finite-time Consensus under Directed Graphs

Abstract This paper focuses on deal with the finite-time consensus with event-triggered control strategy for multi-agent systems (MASs). An event-triggered protocol for finite-time consensus is designed using relative measurements. The coordination measurement error is utilized in the triggering condition design for the purpose of removing the prerequisite of topology graph knowledge. Under strongly connected graph assumptions, by utilizing the proposed consensus protocol, all agents can complete consensus and Zeno behaviour will not happen in a settling time. Next, by decomposing the Laplacian matrix in Frobenius norm form, the results are extended to the more general graphs containing a directed spanning tree. At last, a numerical example demonstrates the validity of the algorithm results.

ROBUST FIXED-TIME CONSENSUS PROTOCOLS FOR MULTI-AGENT SYSTEMS WITH NONLINEAR STATE MEASUREMENTS

This paper solves the robust fixed-time consensus problem for multi-agent systems with nonlinear state measurements. Sufficient conditions are established for the proposed protocol to reach fixed-time consensus under time-varying undirected and fixed directed topology with the aid of Lyapunov functions. It is proved that the finite settling time of the presented protocol for robust consensus is uniformly bounded for any initial condition, which makes it possible for people to design and estimate the convergence time off-line. Numerical simulations are preformed to show the effectiveness of our proposed protocol.

Non-fragile control protocol for finite-time consensus of stochastic multi-agent systems with input time-varying delay

The existence of gain variations in control design often disrupts most of the control system performance. By considering this point, as a first attempt in the literature, a robust non-fragile state feedback control design is proposed in this paper for achieving finite-time consensus in a class of stochastic nonlinear multi-agent systems with randomly occurring uncertainty and randomly occurring nonlinearity. Specifically, the randomness phenomena are characterized with the aid of stochastic variables that satisfy the Bernoulli distribution properties. To design the non-fragile control protocol, the communication graph is chosen to be directed and connected subject to switching topologies. On the basis of the Lyapunov–Krasovskii stability theory and stochastic analysis techniques, a new set of sufficient conditions is established to guarantee that the states of all agents can reach an agreement over a given finite-time period via the proposed non-fragile switched control law. The effectiveness of the designed consensus protocol is demonstrated through an academic example.