Lin Tie

A new class of finite-time nonlinear consensus protocols for multi-agent systems

This paper is devoted to investigating the finite-time consensus problem for a multi-agent system in networks with undirected topology. A new class of global continuous time-invariant consensus protocols is constructed for each single-integrator agent dynamics with the aid of Lyapunov functions. In particular, it is shown that the settling time of the proposed new class of finite-time consensus protocols is upper bounded for arbitrary initial conditions. This makes it possible for network consensus problems that the convergence time is designed and estimated offline for a given undirected information flow and a group volume of agents. Finally, a numerical simulation example is presented as a proof of concept.

Distributed robust finite-time nonlinear consensus protocols for multi-agent systems

This paper investigates the robust finite-time consensus problem of multi-agent systems in networks with undirected topology. Global nonlinear consensus protocols augmented with a variable structure are constructed with the aid of Lyapunov functions for each single-integrator agent dynamics in the presence of external disturbances. In particular, it is shown that the finite settling time of the proposed general framework for robust consensus design is upper bounded for any initial condition. This makes it possible for network consensus problems to design and estimate the convergence time offline for a multi-agent team with a given undirected information flow. Finally, simulation results are presented to demonstrate the performance and effectiveness of our finite-time protocols.

On controllability of two-dimensional discrete-time bilinear systems

In this paper, controllability of two-dimensional discrete-time bilinear systems is studied. Sufficient conditions for the systems to be controllable are presented. In particular, the control inputs are computed to achieve the state transition for the controllable systems by using the root locus technique. Examples are also provided to illustrate the results of the paper.

Remarks on controllability of discrete-time bilinear systems

This paper studies controllability of discrete-time bilinear systems. Based on the existing results, this paper simplifies some proofs on controllability of discrete-time bilinear systems and therefore simplifies the algorithm on solving the control inputs that achieve state transition for the controllable systems. An example is given to show the effectiveness of the simplified proof and algorithm.

Fixed-time consensus for multi-agent systems under directed and switching interaction topology

In this paper, we address the fixed-time consensus problem for multi-agent systems in networks with directed and switching interaction topology. With the introduction of mirror operation, two global distributed nonlinear consensus protocols are constructed for each first-order agent under strongly connected information flow. The distinctive feature of this paper is to address the explicit bounds of the finite settling time for both protocols are independent of initial condition, which makes it possible for network consensus problems of a multi-agent team with guaranteed convergence time. Further, the second protocol is valid for the networks of multi-agents with switching topology provided that the sum of time intervals, in which the information flow is strongly connected, is larger than the estimated upper-bound for settling time. Finally, simulations are provided to demonstrate the performance and effectiveness of our theoretical results.

On small-controllability and controllability of a class of nonlinear systems

In this paper, small-controllability and controllability of a class of nonlinear systems are studied. Both the discrete-time case and continuous-time case are considered. By proposing an implicit function approach, sufficient conditions for the systems respectively to be small-controllable and controllable are obtained. Examples are also provided to illustrate the results of the paper.

On small-controllability of a class of Hammerstein-nonlinear systems – an implicit function approach

In this paper, an implicit function approach is applied to controllability of a class of discrete-time Hammerstein-nonlinear systems. Based on this approach, the systems are shown to own a strong property, namely, small-controllability. As an immediate application, the obtained small-controllability results are generalised to the continuous-time Hammerstein-nonlinear systems and some continuous-time versions of small-controllability are presented.

On controllability of discrete-time multi-input inhomogeneous bilinear systems without drift

In this paper, we consider the controllability problem of discrete-time multi-input inhomogeneous bilinear systems without drift. We first make some discussions on controllability of the systems. We then focus on a special class of the systems, which can be regarded as the most close to multiinput linear time-invariant systems, and obtain a necessary and sufficient condition for controllability. Finally, we provide an example to demonstrate the results of this paper.

Hyperbolic tangent function based adaptive trajectory tracking control for quadrotors

This paper proposes a new adaptive trajectory tracking control algorithm with command filtered compensation for quadrotor aircrafts, that ensures the asymptotic convergence to any desired trajectory in presence of parametric and external uncertainties. The proposed algorithm employs a hyperbolic tangent function matrix to construct a continuous adaptive control law with an online approximator, and integrates a linear tracking-differentiator into the backstepping design to eliminate the timescale separation assumption between attitude and linear dynamics. The stability of the closed-loop control system is proven via the use of Lyapunov theory and Barbalat lemma. Finally, a numerical simulation of tracking a circular trajectory is performed to demonstrate the validity and effectiveness of the proposed algorithm.

On controllability of homogeneous and inhomogeneous discrete-time multi-input bilinear systems in dimension two

ABSTRACT In this paper, the controllability problem of two-dimensional discrete-time multi-input bilinear systems is completely solved. The homogeneous and the inhomogeneous cases are studied separately and necessary and sufficient conditions for controllability are established by using a linear algebraic method, which are easy to apply. Moreover, for the uncontrollable systems, near-controllability is considered and similar necessary and sufficient conditions are also obtained. Finally, examples are provided to demonstrate the results of this paper.