5 research outputs found
Gradient-Free Distributed Optimization with Exact Convergence
In this paper, a gradient-free distributed algorithm is introduced to solve a
set constrained optimization problem under a directed communication network.
Specifically, at each time-step, the agents locally compute a so-called
pseudo-gradient to guide the updates of the decision variables, which can be
applied in the fields where the gradient information is unknown, not available
or non-existent. A surplus-based method is adopted to remove the doubly
stochastic requirement on the weighting matrix, which enables the
implementation of the algorithm in graphs having no associated doubly
stochastic weighting matrix. For the convergence results, the proposed
algorithm is able to obtain the exact convergence to the optimal value with any
positive, non-summable and non-increasing step-sizes. Furthermore, when the
step-size is also square-summable, the proposed algorithm is guaranteed to
achieve the exact convergence to an optimal solution. In addition to the
standard convergence analysis, the convergence rate of the proposed algorithm
with respect to different cases of step-sizes is investigated. Finally, the
effectiveness of the proposed algorithm is verified through numerical
simulations
Periodic event-triggered output regulation for linear multi-agent systems
This study considers the problem of periodic event-triggered (PET)
cooperative output regulation for a class of linear multi-agent systems. The
advantage of the PET output regulation is that the data transmission and
triggered condition are only needed to be monitored at discrete sampling
instants. It is assumed that only a small number of agents can have access to
the system matrix and states of the leader. Meanwhile, the PET mechanism is
considered not only in the communication between various agents, but also in
the sensor-to-controller and controller-to-actuator transmission channels for
each agent. The above problem set-up will bring some challenges to the
controller design and stability analysis. Based on a novel PET distributed
observer, a PET dynamic output feedback control method is developed for each
follower. Compared with the existing works, our method can naturally exclude
the Zeno behavior, and the inter-event time becomes multiples of the sampling
period. Furthermore, for every follower, the minimum inter-event time can be
determined \textit{a prior}, and computed directly without the knowledge of the
leader information. An example is given to verify and illustrate the
effectiveness of the new design scheme.Comment: 17 pages, 13 figures, submitted to Automatica. accepte
Robust finite-time connectivity preserving coordination of second-order multi-agent systems
In this paper, we consider robust finite-time connectivity preserving coordination problems for second-order multi-agent systems with limited sensing range. Based on integral sliding mode control and artificial potential field, a distributed controller is developed to achieve robust finite-time consensus and meanwhile maintain the connectivity of the communication network. The method is further extended to address a finite-time formation tracking control problem. Numerical examples are given to show the effectiveness of the proposed methods.NRF (Natl Research Foundation, S’pore)EDB (Economic Devt. Board, S’pore