Dynamic Electromagnetic Scattering Simulation of Tilt-Rotor Aircraft in Multiple Modes.

To study the electromagnetic scattering of tilt-rotor aircraft during multi-mode continuous flight, a dynamic simulation approach is presented. A time-varying mesh method is established to characterize the dynamic rotation and tilting of tilt-rotor aircraft. Shooting and bouncing rays and the uniform theory of diffraction are used to calculate the multi-mode radar cross-section (RCS). And the scattering mechanisms of tilt-rotor aircraft are investigated by extracting the micro-Doppler and inverse synthetic aperture radar images. The results show that the dynamic RCS of tilt-rotor aircraft in helicopter and airplane mode exhibits obvious periodicity, and the transition mode leads to a strong specular reflection on the rotor's upper surface, which increases the RCS with a maximum increase of about 36 dB. The maximum micro-Doppler shift has functional relationships with flight time, tilt speed, and wave incident direction. By analyzing the change patterns of maximum shift, the real-time flight state and mode can be identified. There are some significant scattering sources on the body of tilt-rotor aircraft that are distributed in a planar or point-like manner, and the importance of different scattering sources varies in different flight modes. The pre-studies on the key scattering areas can provide effective help for the stealth design of the target.

Sampled-Data Asynchronous Control for Switched Nonlinear Systems With Relaxed Switching Rules.

This article investigates the problem of quantized sampled-data control for continuous-time switched Takagi-Sugeno (T-S) fuzzy systems with the asynchronous phenomenon. First, considering that the system and controller modes could not be perfectly synchronized all the time, we study possible cases of mode mismatching by exploiting the average dwell time (ADT) switching strategy. Since the fact that a minimum dwell time of each subsystem is not required in the ADT switching rule, multiple system switching is allowed within one sampling interval, which overcomes the limitation of at most once switching during any sampling interval in existing works. Second, the asynchronous premise variables between the fuzzy system and fuzzy controller are taken into consideration in the quantized sampled-data control scheme. Then, by virtue of the Lyapunov function approach, we obtain sufficient conditions to guarantee that the asynchronously switched T-S fuzzy system is exponentially stable with quantized sampled-data input. Furthermore, the weighted L2 -gain is discussed for the system under external disturbance, and an H∞ state feedback controller is correspondingly designed with prescribed disturbance attenuation. Finally, the validity and advantage of the proposed methods are illustrated by two examples.

Zonotopic Fault Detection for 2-D Systems Under Event-Triggered Mechanism.

This article studies the problem of event-triggered fault detection (FD) for 2-D systems subjected to amplitude-bounded exogenous disturbance and measurement noise via a zonotopic residual evaluation mechanism. An event-triggered mechanism is introduced into the FD framework to save limited communication resources. A finite-frequency (FF) mixed l∞/h∞ index is derived to ensure the residual signal is sensitive to a fault signal while robust to disturbance and noise, based on which an optimal mixed l∞/h∞ FD filter design criterion is provided. Instead of constant thresholds, novel zonotope-based dynamic thresholds are utilized for residual evaluation. Finally, simulation results are presented to illustrate the effectiveness of the developed mechanism.

Filtering for Switched T-S Fuzzy Systems With Persistent Dwell Time.

The H∞ filter design for a class of switched Takagi-Sugeno (T-S) fuzzy systems with persistent dwell time (PDT) is investigated in this paper. The considered switched fuzzy systems contain a limited number of subsystems and each local subsystem is represented by the well-known T-S fuzzy model. Compared with the dwell time (DT) switching or average DT switching that attracted quantities of interests over the last decade, the PDT switching considered in this paper is known to be more general. The stability and L 2 -gain analysis for switched systems with PDT switching are derived first, based on which a set of full-order H∞ filter is designed to guarantee the global uniform asymptotic stability with a prescribed nonweighted H∞ noise attenuation performance for the resulting filtering error system. Finally, the effectiveness of the provided method is illustrated with an example.

Exponential Synchronization of Networked Chaotic Delayed Neural Network by a Hybrid Event Trigger Scheme.

This paper is concerned with the exponential synchronization for master-slave chaotic delayed neural network with event trigger control scheme. The model is established on a network control framework, where both external disturbance and network-induced delay are taken into consideration. The desired aim is to synchronize the master and slave systems with limited communication capacity and network bandwidth. In order to save the network resource, we adopt a hybrid event trigger approach, which not only reduces the data package sending out, but also gets rid of the Zeno phenomenon. By using an appropriate Lyapunov functional, a sufficient criterion for the stability is proposed for the error system with extended ( , , )-dissipativity performance index. Moreover, hybrid event trigger scheme and controller are codesigned for network-based delayed neural network to guarantee the exponential synchronization between the master and slave systems. The effectiveness and potential of the proposed results are demonstrated through a numerical example.