A neural network-based direct adaptive fault tolerance flight control for control surface damage

AbstractIn order to enhance the reliability of flight control systems, a new neural network-based direct adaptive fault tolerance control was proposed for flight control system in the presence of control surface damage. Based on the accuracy approach of neural network, a fault parameter identification models were built to constitute hybrid compensator in order to ensure the strictly positive real of the failure flight control systems in the inner control loop. In the outer loop, a common direct adaptive controller was designed. The scheme was illustrated through simulations using an aircraft. The results show that an aircraft has also good dynamic performance in the control surface damage

Eliminating Via-Plane Coupling using Ground Vias for High-Speed Signal Transitions

When a high-speed signal transits through a via that penetrates a plane pair, parallel-plane resonances can cause additional insertion loss for the signal. To eliminate this via-plane coupling, ground vias are added adjacent to the signal via. This paper discusses the impact of the ground vias as a function of the number of the ground vias, their locations, and the size of the plane pair. A block-by-block physics-based equivalent circuit modeling approach is used in the study. The underlying physics of the phenomenon and the design implications are also discussed in the paper

Differential Signalling in PCBs: Modeling and Validation of Dielectric Losses and Effects of Discontinuities

This paper focuses on differential signal transmission above ground planes with gaps, taking into account the dielectric and conductive losses of the substrate. An equivalent lumped-circuit is proposed and its suitability is investigated by comparing the obtained numerical results with the measured data. Furthermore the differential to common mode conversion of the waves, while crossing the gap, is theoretically analyzed and experimentally verified

Efficient Modeling of Discontinuities and Dispersive Media in Printed Transmission Lines

The finite-difference time-domain method is applied to the analysis of transmission lines on printed circuit boards. The lossy, dispersive behavior of the dielectric substrate is accurately accounted for by means of several algorithms whose accuracy is discussed and compared. Numerical results are validated by comparisons with measurements and an equivalent circuit of slot in the ground plane is proposed

Evolution of Maximum Bending Strain on Poisson's Ratio Distribution

In recent years, new flexible functional materials have attracted increasing interest, but there is a lack of the designing mechanisms of flexibility design with superstructures. In traditional engineering mechanics, the maximum bending strain (MBS) was considered universal for describing the bendable properties of a given material, leading to the universal designing method of lowering the dimension such as thin membranes designed flexible functional materials.In this work, the MBS was found only applicable for materials with uniformly distributed Poisson's ratio, while the MBS increases with the thickness of the given material in case there is a variation Poisson's ratio in different areas. This means the MBS can be enhanced by certain Poisson's ratio design in the future to achieve better flexibility of thick materials. Here, the inorganic freestanding nanofiber membranes, which have a nonconstant Poisson's ratio response on stress/strain for creating nonuniformly distributed Poisson's ratio were proven applicable for designing larger MBS and lower Young's modulus for thicker samples

Differential signal characterization, VNA calibration and loss extraction of transmission lines

Differential circuits are becoming increasingly important in radio frequency (RF) and microwave applications. This has led to the development of mixed-mode scattering parameters to address differential and common-mode operations. Mixed-mode scattering parameters also address the conversion between the two modes of operation. In the measurement or in the modeling of any differential circuits, it is found that a pure-mode network-analyzer provides accurate measurements of differential circuits. Additionally, given the standard S-parameters (either by measurements or by modeling), we can apply a conversion from standard S-parameters to mixed-mode S-parameters. Furthermore, to guarantee the accuracy of the S-parameters derived from the measurement by the network analyzer, a proper calibration method and an appropriate type of system error model must be carefully considered. In this thesis, several different normal calibration standards, including TRL, TRL*, TRM and TRM*, and their related error models are analyzed. Single-ended and mixed-mode S-parameters can be further processed to generate time domain eye patterns, so as to characterize signal loss and attenuation through RF devices and interconnects. The method of eye pattern generation is discussed and some samples of eye patterns for different high data-rate transmissions are presented. Another part of the thesis details the modeling of frequency-dependent losses on transmission lines. A methodology for extracting the dielectric constant and loss tangent of the PCB substrate is demonstrated using stripline test structures. Some works on transmission line characterization and cross-section analysis are also discussed --Abstract, page iii

Modeling of Multiple Vias with a Shared Anti-Pad in an Irregular Plate Pair using Domain Decomposition Approach

An irregular plate pair with multiple vias sharing an anti-pad is decomposed into top/bottom plate-thickness domain and parallel-plate domain whose admittance matrices are calculated by three-dimensional (3D) finite element method (FEM) and hybrid 3D/2D FEM. Combined admittance matrix algorithm is used to obtain the final admittance matrix of the plate pair including finite thickness plates. The widely-used assumption of transverse electromagnetic (TEM) modes on anti-pads is carefully investigated by comparing the combined admittance matrix algorithm with hybrid 3D/2D FEM. It is found that higher-order modes are excited on anti-pads and in practical printed circuit board, the higher-order modes can penetrate from one layer of plate pair to another layer. This may provide guidance for future research for multiple vias in a shared anti-pad