Yu-Ping Tian

Consensus of Multi-Agent Systems With Diverse Input and Communication Delays

The consensus problem for multi-agent systems with input and communication delays is studied based on the frequency-domain analysis. Two decentralized consensus conditions are obtained, one of which is given for the systems based on undirected graphs with diverse input delays and the other is for the systems based on directed graphs with diverse communication delays and input delays. For the systems with both communication delays and input delays, the consensus condition is dependent on input delays but independent of communication delays.

Brief paper: Consentability and protocol design of multi-agent systems with stochastic switching topology

This paper studies the mean square consentability problem for a network of double-integrator agents with stochastic switching topology. It is proved that in Markov-switching topologies, the network is mean square consentable under linear consensus protocol if and only if the union of graphs in the switching topology set has globally reachable nodes. A necessary and sufficient condition of the mean square consensus is obtained. Finally, an LMI approach to the design of the consensus protocol is presented. Numerical simulations are given to illustrate the results.

Brief paper: Robust consensus of multi-agent systems with diverse input delays and asymmetric interconnection perturbations

The consensus problem of second-order multi-agent systems with diverse input delays is investigated. Based on the frequency-domain analysis, decentralized consensus conditions are obtained for the multi-agent system with symmetric coupling weights. Then, the robustness of the symmetric system with asymmetric perturbation is studied. A bound of the largest singular value of the perturbation matrix is obtained as the robust consensus condition. Simulation examples illustrate the design procedure of consensus protocols and validate the correctness of the results.

Brief Exponential stabilization of nonholonomic dynamic systems by smooth time-varying control

A general dynamic model is proposed for describing a large class of nonholonomic systems including extended chained systems, extended power systems, underactuated surface vessel systems etc. By introducing an assistant state variable and a time-varying state transformation based on the concept of minimal dilation degree, this class of nonholonomic systems is transformed into linear time-varying control systems, and the asymptotic exponential stability is thus achieved by using a smooth time-varying feedback control law. The existence and uniqueness of the minimal dilation degree for the discussed systems are also proved under certain conditions.

Consensus of Data-Sampled Multi-Agent Systems With Random Communication Delay and Packet Loss

The consensus problem is considered for a team of second-order mobile agents communicating via a network with noise, variable delays and occasional packet losses. A queuing mechanism is applied and the switching process of the interaction topology of the network is modeled as a Bernoulli random process. In such a framework, a necessary and sufficient condition is presented for the mean-square robust consensus. Moreover, a necessary and sufficient condition of the solvability of the mean-square robust consensus problem is established. An approach to designing consensus protocol is proposed and numerical examples are given to illustrate the results.

Finite-time stability of cascaded time-varying systems

The uniform global finite-time stability is discussed for a cascaded time-varying system consisting of two uniformly finite-time stable subsystems. It is shown that a forward completeness condition is enough to ensure the uniform global finite-time stability of the system. For ease of reference, a particular result with a growth rate condition is also deduced. These stability results are applied to the tracking control problem of a non-holonomic wheeled mobile robot in kinematic model. Two tracking control laws are developed respectively for two different cases of the desired rotate velocity. Both control laws are continuous and can control the mobile robot to track the desired trajectory in finite time. Simulation results are provided to show the effectiveness of the method.

Brief paper: High-order consensus of heterogeneous multi-agent systems with unknown communication delays

This paper studies the high-order consensus problem for heterogeneous multi-agent systems with unknown communication delays. It is shown that high-order consensus may exist in systems with heterogeneous agents. A necessary and sufficient condition is given for the existence of high-order consensus solution to heterogeneous multi-agent systems. The obtained condition shows that for systems with diverse communication delays, high-order consensus does not require each self-delay of agent is equal to the corresponding communication delay. A matching condition for self-delays and communication delays is derived. Finally, when communication delays are unknown, an adaptive adjustment mechanism is proposed for on-line adjusting self-delays.

Formation control of multi-agent systems with heterogeneous communication delays

In this article, the formation control is investigated for a network of second-order dynamic agents with heterogeneous communication delays. The desired stationary formation is achieved by introducing diverse self-delay for each agent. In addition, a delay-dependent formation control algorithm is proposed to achieve the desired moving formation. Based on the frequency-domain analysis and matrix theory, sufficient conditions are obtained for the multi-agent systems asymptotically converging to desired stationary and moving formations, respectively. Simulation results illustrate the correctness of the results.

Finite time synchronization of chaotic systems

Abstract Using finite time control techniques, continuous state feedback control laws are developed to solve the synchronization problem of two chaotic systems. We demonstrate that these two chaotic systems can be synchronized in finite time. Examples of Duffing systems, Lorenz systems are presented to verify our method.

Global stabilization of rigid formations in the plane

This paper considers the problem of distributed control of rigid formation shapes in the plane for multi-agent systems. A constructive perturbation method is proposed and combined with the conventional gradient control law. The proposed control law stabilizes the desired rigid formation in a global sense for all initial conditions except the case when a pair of communicating agents happen to have the same initial location. It also avoids collisions between any two communicating agents during the motion. Simulation results are provided to illustrate the effectiveness of the control algorithm.