The Swarm in situ Ne and Te measurements are used for the first time to investigate the plasma irregularities inside the MIT. The auroral particle precipitations dominate the dayside MIT region irregularities. The temperature gradient drift instability contributes mostly to the nightside MIT region irregularities.
In this paper, the problem of preview tracking control for a class of discrete-time nonlinear Lur’e systems is investigated. To overcome the difficulty arising from the sector nonlinearity, the original system is transformed into a linear parameter varying (LPV) system, and a new auxiliary method is introduced. The difference between the state vector and the auxiliary variable is used instead of the usual difference between system states. At the same time, the tracking error and the previewable future reference information are also considered in order to construct an augmented error system (AES). Then, the preview tracking problem is reduced to a robust control problem. Note that the AES is still an LPV system. Next, a state feedback controller is developed to ensure that the closed-loop system is asymptotically stable with H∞ guaranteed cost performance. Based on this, a preview controller for the original system is proposed. Finally, two numerical examples are provided to illustrate the effectiveness of the controller.
The problem of observer‐based decentralized robust H∞ output tracking control with preview action in a class of uncertain and disturbed nonlinear interconnected systems is investigated in this study. The considered interconnected system consists of several subsystems with nonlinear interconnections, parametric uncertainties, and external disturbances. Based on the augmented error system approach combined with Lyapunov stability theory and special matrix inequality linearization techniques, a sufficient condition for the existence of a decentralized observer‐based robust H∞ output feedback preview controller is derived for the original interconnected system in terms of linear matrix inequality (LMI) formulations. The gain matrices of the tracking controller and state observer are derived using only a one‐step LMI procedure, which overcomes the drawbacks of some multistep iterative algorithms. Finally, the effectiveness of the proposed control scheme is validated using a numerical example.
In the fault-tolerant control theory based on model following control, the desired signal of the control system is the output of a reference system. This paper is concerned with the design of preview controller for a class of fault systems. A composite vector is introduced by including error vector, fault system state vector and reference system state vector. Then, we derived an augmented system from the known system equation, in which the reference input has equal status with the desired signal in the traditional preview control theory. Therefore, we can use the known theory to design the preview controller for augmented system, then the preview controller of the original fault system can be obtained by integration method. This paper strictly discusses the connection between stabilization and detectability of the augmented system and the corresponding characteristics of the original system. Finally, by applying this theory to a real steam generator water level control system, it is found that the actions of the reference input preview and the fault signal preview can effectively eliminate the effect of the fault signal on the water level of the steam generator. The simulation shows the effectiveness of the controller designed.
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