Shicheng Wang

Decentralized adaptive attitude synchronization of spacecraft formation

Abstract This paper studies adaptive attitude synchronization of spacecraft formation with possible time delay. By introducing a novel adaptive control architecture, decentralized controllers are developed, which allow for parameter uncertainties and unknown external disturbances. Based upon graph theory, Lyapunov stability theory and time-delay control theory, analytical tools are also provided. A distinctive feature of this work is to address the adaptive attitude synchronization with unknown parameters and coupling time delay in a unified theoretical framework, with general directed information flow. It is shown that arbitrary desired attitude tracking and synchronization with respect to a given reference can be attained. Simulation results are provided to demonstrate the effectiveness of the obtained results.

Distributed consensus of a class of networked heterogeneous multi-agent systems

Abstract 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 Barbalats Lemma, the stability of the controllers is proved. Simulation results are also provided to illustrate the effectiveness of the obtained results.

Distributed Adaptive Consensus for Multiple Mechanical Systems with Switching Topologies and Time-varying Delay

Abstract 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.

Recursive depth parametrization of monocular visual navigation: Observability analysis and performance evaluation

Abstract In this paper, the theoretical and practical feasibility of estimating ego-motion in monocular navigation is under investigation. In particular, this paper concerns the observability issues of monocular navigation models. In order to recover the ego-motion of the monocular camera from 2D (two-dimension) image sequence, this paper proposes a novel recursive parametric model. This model differs from other traditional parametric models with the reduced state-dimension and the consistent observability of system state. In addition, the consistent observability of different models are compared by using time-varying observability analysis theory. At the end of this paper, two groups of experiments are implemented to validate the effectiveness of the proposed method.

Consensus of Nonlinear Multi-agent Systems with Self and Communication Time Delays: A Unified Framework

Abstract In this paper, we study the consensus problem of multi-agent systems with parametric uncertainties on directed graph communication topologies containing a spanning tree. The challenge lies in that the input–output property of a strictly proper system transfer function involving self and communication delays and the extremum of a delay-involved transfer function are both unclear. By establishing a new input–output property of the delay-involved strictly proper transfer function and applying a constructive approach in frequency domain, we obtain the extremum of the delay-involved transfer function, upon which, we establish a unified framework to resolve the consensus problem of multi-agent systems with parametric uncertainties and time delays, and the terminal convergence point value is achieved. Based upon Lyapunov stability theory and frequency domain input–output analysis, we demonstrate that the proposed unified consensus control framework ensures scaled weighted average consensus with the integral action of the synchronization signal vector. Simulation results are provided to demonstrate the effectiveness of the proposed consensus scheme.

Coordination Control of Networked Euler-Lagrange Systems with Possible Switching Topology

Abstract This paper studies adaptive coordination control of Euler-Lagrange (EL) systems with unknown parameters in system dynamics and possible switching topology. By introducing a novel adaptive control architecture, decentralized controllers are developed, which allow for parametric uncertainties. Based upon graph theory, Lyapunov theory and switching control theory, the stability of the proposed algorithms are demonstrated. A distinctive feature of this work is to address the coordination control of EL systems with unknown parameters and switching topology in a unified theoretical framework. It is shown that both static and dynamic coordinations can be reached even when the communication is switching. Simulation results are provided to demonstrate the effectiveness of the obtained results.

Simultaneous estimation of ego-motion and vehicle distance by using a monocular camera

Auto navigation and vehicle distance estimation are of the critical importance in intelligent vehicles. This paper proposes a novel approach to solve these two problems simultaneously by using a monocular camera. First, we introduce an incremental depth parameterized model to overcome the scale ambiguity problem in monocular vision, which differs from other parameterized models with reduced state-dimension and consistent observability. In addition, the view-field of camera is divided into static and dynamic parts so that the egomotion and vehicle-space can be calculated simultaneously. Outdoor experiments are implemented to validate the effectiveness of the proposed approach.

Performance enhancement of large-ship transfer alignment : a moving horizon approach

In shipborne Transfer Alignment (TA) applications, partial observability is one of the mostimportant factors limiting convergence velocity. This paper proposes a new method ofattributing weak observable states and lever-arm variables to a group of constraints in orderto improve the observability of TA model. This yields the so-called Constrained TransferAlignment (CTA) model which is uniformly observable even under zero-manoeuvre con-ditions. Within this framework, the Moving Horizon Estimation (MHE) and its stabilityanalysis are also addressed. Finally, comparative simulation results are given to demonstratethe advantages of the proposed approach.KEY WORDS

Distributed finite-time attitude containment control of multi-rigid-body systems

Abstract In this paper, we study the distributed finite-time attitude containment control problem for multi-rigid-body systems with multiple stationary and dynamic leaders under directed graphs. Based upon two sliding mode observation vectors, the input torque is designed to achieve the control goal. In the regulation case, all the followers will converge into the attitude convex hull spanned by the leaders in finite time, while in the dynamic leaders case, not only the attitudes but also the attitude derivatives of the followers will converge into the convex hull of the leaders in finite time. Necessary and sufficient criteria are established for both the two protocols. Finally, all the theoretical results are illustrated by numerical simulations.

Consensus for multiple heterogeneous Euler–Lagrange systems with time-delay and jointly connected topologies

Abstract 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.