Distributed Cooperative Anti-Disturbance Control for High-Order MIMO Nonlinear Multi-Agent Systems

To solve the synchronization and tracking problems,a cooperative control scheme is proposed for a class of higher-order multi-input and multi-output(MIMO)nonlinear multi-agent systems(MASs)subjected to uncertainties and external disturbances.First,coupled relationships among Laplace matrix,leader-following adjacency matrix and consensus error are analyzed based on undirected graph.Furthermore,nonlinear disturbance observers(NDOs)are designed to estimate compounded disturbances in MASs,and a distributed cooperative anti-disturbance control protocol is proposed for high-order MIMO nonlinear MASs based on the outputs of NDOs and dynamic surface control approach.Finally,the feasibility and effectiveness of the proposed scheme are proven based on Lyapunov stability theory and simulation experiments.

Model-free adaptive robust control method for high-speed trains

Aiming at the robustness issue in high-speed trains(HSTs)operation control,this article proposes a model-free adaptive control(MFAC)scheme to suppress disturbance.Firstly,the dynamic linearization data model of train system under the action of measurement disturbance is given,and the Kalman filter(KF)based on this model is derived under the minimum variance estimation criterion.Then,according to the KF,an anti-interference MFAC scheme is designed.This scheme only needs the input and output data of the controlled system to realize the MFAC of the train under strong disturbance.Finally,the simulation experiment of CRH380A HSTs is carried out and compared with the traditional MFAC and the MFAC with attenuation factor.The proposed control algorithm can effectively suppress the measurement disturbance,and obtain smaller tracking error and larger signal to noise ratio with better applicability.

A class of second-order sliding mode controller for servo systems

Sliding mode control （SMC） has been widely investigated in recent years. In this paper, a class of second- order SMC is proposed and used to achieve good tracking performance in servo systems. SMC has good robustness to the disturbances, but conventional SMC uses a sign function to drive the error on the sliding surface, which could generate chattering effect. In order to avoid this problem, our improved SMC uses the integral of the sign function. Coupled with an exponential reaching law, the new SMC can better suppress torque disturbances and chatter, This paper first gives the derivation of the new SMC. Simulation and experimental results are then carried out to demonstrate its tracking performance and robustness against torque disturbance and chatter.

Impact of external optical feedback on the beat notes of dual-polarization fiber lasers

We present a theoretical analysis and an experimental study of the impacts of external optical feedback on dualfrequency fiber lasers. The external optical feedback can effectively suppress the phase noise of the beat notes of dual-frequency fiber lasers, provided some requirements are satisfied. The polarization of the optical feedback is important for the fiber laser＇s stability, and it can also tune the beat note frequency. A side effect of external optical feedback, as demonstrated in the experiments, is lowering the sensitivity of the dual-frequency fiber laserbased sensors, although such degradation is not obvious.