Search

In this paper, we consider the consensus problem of multiple agents modeled by Euler–Lagrange (EL) equation, among which two classes of agents are addressed, i.e., some agents with exactly known parameters and the others with parametric uncertainties. We propose a distributed consensus protocol for the heterogeneous EL systems in which both time-delay and jointly connected topologies are taken into consideration. Based on graph theory, Lyapunov theory and Barbalat׳s lemma, the stability of the controller is proved. A distinctive feature of this work is to investigate the consensus problem of EL systems with heterogeneous dynamics, time-delay and jointly connected topologies in a unified theoretical framework. Simulation results are also provided to illustrate the effectiveness of the obtained results.

In this paper, we consider the consensus problem of a class of heterogeneous multi-agent systems composed of the linear first-order and second-order integrator agents together with the nonlinear Euler–Lagrange (EL) agents. First, we propose a distributed consensus protocol under the assumption that the parameters of heterogeneous system are exactly known. Sufficient conditions for consensus are presented and the consensus protocol accounting for actuator saturation is developed. Then, by combining adaptive controller and PD controller together, we design a protocol for the heterogeneous system with unknown parameters (in the nonlinear EL dynamics). Based on graph theory, Lyapunov theory and Barbalat's Lemma, the stability of the controllers is proved. Simulation results are also provided to illustrate the effectiveness of the obtained results.

This paper studies the adaptive consensus problem of networked mechanical systems with time-varying delay and jointly-connected topologies. Two different consensus protocols are proposed. First, we present an adaptive consensus protocol for the connected switching topologies. Based on graph theory, Lyapunov stability theory and switching control theory, the stability of the proposed algorithm is demonstrated. Then we investigate the problem under the more general jointly-connected topologies, and with concurrent time-varying communication delay. The proposed consensus protocol consists of two parts: one is for the connected agents which contains the current states disagreement among them and the other is designed for the isolated agents which contains the states difference between the current and past. A distinctive feature of this work is to address the consensus control problem of mechanical systems with unknown parameters, time-varying delay and switching topologies in a unified theoretical framework. Numerical simulation is provided to demonstrate the effectiveness of the obtained results.

In this paper, we study the leader-following attitude consensus problem for multi-rigid-body systems under jointly connected topologies coupled with time-varying communication delays. By associating an auxiliary vector for each follower, the control algorithm is designed, and the stability of the whole system is proved by using Lyapunov Krasovskii function and contradiction method. In terms of linear matrix inequalities, we derive sufficient conditions that guarantee all followers asymptotically converge to the leader.

In this paper, a fuzzy dynamic characteristic modeling and adaptive control method is proposed for a class of nonlinear systems. By employing fuzzy dynamic characteristic model, the controlled plant is described as a slowly time-varying fuzzy system, wherein the parameters are estimated online by using recursive Least- Squares algorithm. Under this framework, a fuzzy adaptive controller is constructed, and the stability condition of the closed-loop system is also derived. The main advantage of the proposed method lies in no requirement for the prior knowledge of system model and less parameters to tune, which allows engineers to operate it in a simple, straightforward manner. The proposed method is applied to the control of hypersonic vehicle, and simulation results are given to demonstrate the effectiveness of the obtained results.

In this paper, the spacecraft formation control and its stability problems are studied on the basis of the energy concept. The formation systems are viewed as a multi-mass point system with both generalized elastic deformation and rigid body movement, and certain potential fields interact with each other within the formation. Consequently, the stability of formation and coordination and the controller design problems are studied from the perspectives of energy. The symmetry in formation motion is studied, and the definition of formation stability and its corresponding criteria are presented based upon the notion of relative equilibrium. Then, the artificial potential method is explored to design the formation control law, and the stability of which is followed by utilizing the former criterions. The effectiveness of the proposed formation control approach is also demonstrated by numerical results.

This paper deals with the performance improvement of force feedback in bilateral teleoperation with PD controller. In traditional PD structures, the force feedback is simply determined by the position and velocity of the master and the slave manipulators, which may induce large resistance forces to the operator even in free motion. In this paper, a novel PD bilateral controller is proposed to tackle this problem. By incorporating a distance variable in the controller, we show that the appropriate force feedback can be obtained which still guarantees the system stability. To validate the proposed algorithm, an experiment is also carried out on our single degree of freedom teleoperation system. The results indicate that this strategy is effective for safe teleoperation missions.

We address the problem of tracking relative translation in a leader-follower spacecraft formation architecture using Robust Integral of the Sign Error (RISE) based Neural Network (NN) technique. Based on the relative translational dynamic model of the spacecraft formation, RISE is introduced to approximate the dynamics of the follower as well as various practical disturbances. It is shown that the errors of the entire formation closed-loop are asymptotical stability (AS), which takes significant advantage over the typical Uniformly Upper Bounded (UUB) property of most NN controllers in high-precision formation tasks. Finally, numerical simulation is provided to verify the effectiveness of the proposed algorithm.