Yang-Yang Chen

A curve extension design for coordinated path following control of unicycles along given convex loops

This article utilises a dynamic model of unicycles to address the convergence of vehicle formation about closed convex curves. A novel curve extension method, extending the target loop along the vector from the loop centre to the point on the loop, is proposed to construct a family of level curves and the existence of a loop function on a tubular-like neighbourhood is proved by referring to the tubular neighbourhood theorem. Path following control is derived based on the loop function which incorporated into the arc-length function to propose the solution to coordinated formation control. We show how backstepping technique, Lyapunov-based theory and graph theory can be combined together to construct the coordinated path following controller under the bidirectional commutation topology. It is proved that the designed cooperative control system is asymptotically stable if the graph is connected. The proposed method is effective for a skewed superellipse, which is a type of curve that includes circles, ellipses and rounded parallelograms.

Coordinated orbit-tracking control of second-order non-linear agents with directed communication topologies

ABSTRACT This paper deals with two-dimensional and three-dimensional cooperative control of multiple agents formation tracking a set of given closed orbits, where each agent has intrinsic second-order non-linear dynamics and the communication topology among agents is directed. By using our previous curve extension method, the cooperative control system can be regarded as a cascade system composed of the orbit-tracking subsystem and the formation subsystem with the orbit-tracking error as input. A novel solution is established by separatively designing the orbit-tracking control law and the formation control protocol ignoring the perturbation at first and then applying input-to-state stability theory to analyse the asymptotic stability of the cascade system. It is shown that the closed-loop system is asymptotic stability if the directed communication topology contains a directed spanning tree. The effectiveness of the analytical results is verified by numerical simulations.

Coordinated path-following and attitude control for multiple surface vessels via curve extension method

This paper addresses the problem of coordinated path-following and attitude control design for a group of fully actuated surface vessels on given convex loops. By incorporating the curve extension design with the consensus-based design we propose a solution to the formation and attitude coordination control. It removes the assumption of nonzero total speed of each vessel that is presented in the literature. With the help of invariance-like theorem and the extension of Barbalats lemma, it is proved that the designed cooperative control system is asymptotically stable if the bidirectional commutation topology is connected. An simulation example is presented as a proof of concept.

Coordinated adaptive control for coordinated path-following surface vessels with a time-invariant orbital velocity

This article considers the problem of directing a family of fully actuated surface vessels to cooperatively follow a set of convex and closed orbits with a time-invariant reference orbital velocity and maintain attitude synchronization. A consensus-based adaptive control law under a bidirectional communication topology is proposed to estimate the reference orbital velocity so that the restriction that every vessel in the family must have access to the reference in the previous literature can be removed. The assumption of nonzero total linear speed of each vessel is removed by the use of potential function. Simulation results demonstrate the effectiveness of the proposed approach.

Cooperative control of multi-agent moving along a set of given curves

This paper deals with a cooperative control problem of a team of double-integrator agents moving along a set of given curves with a nominated formation. A projection-tracking design method is proposed for designing the path-following control and the formation protocol, which guarantee formation motion of the multi-agent system under a directed communication graph. Necessary and sufficient conditions of the control gains for solving the coordinated problem are obtained when the directed communication graph has a globally reachable node. Simulation results of formation motion among three agents demonstrate the effectiveness of the proposed approach.

An adaptive backstepping design for formation tracking motion in an unknown Eulerian specification flowfield

Abstract This paper considers the problem of directing second-order agents tracking a family of simple, closed curves and maintaining a spatiotemporal formation in an unknown spatiotemporal flowfield, where the description of flowfield is Eulerian specification that includes almost all of flowfields in the literature (e.g. the uniform, constant wind, the uniform rotating flowfield and the parameterizable flowfield). Adaptive backstepping technology is first applied with our previous geometric extension to construct the robust formation tracking control and then combined with consensus to propose a new adaptive estimator for the unknown flow speed vector. It is proved that the designed cooperative control system is asymptotically stable if the communication topology is connected. Simulation results are given to verify the theoretical analysis.

Spherical formation tracking control of second-order nonlinear agents with directed communication

This article proposes a solution to the problem of forcing multiple agents to formation tracking a family of given concentric spheres when the communication topology is directed. Each agent under consideration has intrinsic second-order nonlinear dynamics. By using our previous concentric compression method, the cooperative control system can be regarded as a cascade system composed of the spherical tracking subsystem and the formation subsystem with the spherical tracking error as input. The algorithm for directed interaction is constructed by separately designing the control input projected onto the normal vector to the surface of sphere and the direction of spherical meridian for the spherical tracking subsystem, and the control input projected onto the direction of spherical parallel for formation motion. The asymptotic stability of the system is proved by using the tools of Input-to-State stability (ISS) theory. The effectiveness of the analytical results is verified by numerical simulations.

A geometric extension design for second-order nonlinear agents formation surrounding a sphere

This article deals with the problem of driving a family of second-order nonlinear agents to land on a sphere and formation tracking a set of given orbits on the sphere. A novel geometric extension called the concentric compression method is proposed to give a solution to spheral landing and then combines with the control of spherical meridian and parallel to achieve formation motion along given orbits on the sphere. The asymptotic stability of system is proved by Lyapunov-based method when the communication topology is bidirectional. The effectiveness of the analytical result is verified by a numerical simulation.

Distributed filtering based on weighted average strategy in unreliable sensor networks

This paper studies the distributed filtering problem of heterogeneous sensor networks. The communications among sensors and the sensing links are unreliable and randomly lost. Based on Kalman filtering algorithm and weighted average strategy, a sub-optimal filtering algorithm is proposed. The statistical convergence properties of estimation error covariances are investigated and a necessary and sufficient convergence condition is proposed based on LMIs. A special network with sensing link losses is further studied and an explicit necessary convergence condition concerning the observability of sensors and sensing link loss probability is given. Simulation examples are given to illustrate the results.

Coordinated Closed-Curve Path Following Control of Multi-Unicycle in a Time-Invariant Flow Field

Abstract This paper utilizes a dynamic model of unicycles to address the stabilization of formation motion around closed curves in the presence of a time-invariant flow field. It is shown that our previous concentric compression design can be extended to deal with robust coordinated path following control for fighting against the external flow field. Linear acceleration control for each unicycle is added and combined with the rotation control to achieve both temporal and spatial formation in the case of a spatially variable flow, which breaks the restriction of temporally balanced formation relied solely on the angle control in the literature. A potential function is introduced to force each unicycles speed greater than the magnitude of flow. The theoretical result is proved by a numerical example.