Current Issue : October - December Volume : 2016 Issue Number : 4 Articles : 6 Articles
In this article, an improved particle filter with electromagnetism-like mechanism algorithm is proposed for aircraft engine\ngas-path component abrupt fault diagnosis. In order to avoid the particle degeneracy and sample impoverishment of normal\nparticle filter, the electromagnetism-like mechanism optimization algorithm is introduced into resampling procedure,\nwhich adjusts the position of the particles through simulating attractionââ?¬â??repulsion mechanism between charged particles\nof the electromagnetism theory. The improved particle filter can solve the particle degradation problem and ensure the\ndiversity of the particle set. Meanwhile, it enhances the ability of tracking abrupt fault due to considering the latest measurement\ninformation. Comparison of the proposed method with three different filter algorithms is carried out on a univariate\nnonstationary growth model. Simulations on a turbofan engine model indicate that compared to the normal\nparticle filter, the improved particle filter can ensure the completion of the fault diagnosis within less sampling period\nand the root mean square error of parameters estimation is reduced....
We computed magnetic field gradients at satellite altitude, over Europe with emphasis on the Kursk Magnetic Anomaly (KMA). They were calculated using the CHAMP satellite total magnetic anomalies. Our computations were done to determine how the magnetic field observations data from the new ESA/Swarm satellites could be utilized to determine the structure of the magnetization of the Earth�s crust, especially in the region of the KMA. Ten years of CHAMP data were used to simulate the Swarm data. An initial east magnetic anomaly gradient map of Europe was computed and subsequently the North, East and Vertical magnetic gradients for the KMA region were calculated. The vertical gradient of the KMA was also determined using Hilbert transforms. Inversion of the total KMA was derived using Simplex and Simulated Annealing algorithms. The depths of the upper and lower boundaries are calculated downward from the 324 km elevation of the satellite. Our resulting inversion depth model is a horizontal quadrangle. The maximum errors are determined by the model parameter errors....
This article numerically investigates the effects of revolute joint clearance and structural flexibility on the overall dynamic\ncharacteristics of a deployable solar array system. Considering torque spring, close cable loop configuration, and lock\nmechanism, a typical mechanism composed of a main body with a yoke and two panels is used as a demonstration case\nto study the effects of clearance and flexibility on the dynamic response of the deployable solar array system in the\ndeployment and lock process. The normal contact force model and tangential friction model in clearance joint are established\nusing Lankarani Nikravesh model and modified Coulomb friction model, respectively. The numerical simulation\nresults reveal that the coupling of clearance and flexibility makes different effects on the dynamic characteristics of the\ndeployable space solar arrays for different operation stages. Besides, the clearance and flexibility of a mechanical system\nplay crucial roles in predicting accurately the dynamic response of the system, which is the foundation of mechanism\ndesign, precision analysis, and control system design....
An experimental analysis of Global Positioning System (GPS) flight data collected on board a Small Unmanned Aerial Vehicle\n(SUAV) is conducted in order to demonstrate that post processed kinematic Precise Point Positioning (PPP) solutions with\npre cisions approximately 6 cm 3D Residual Sum of Squares (RSOS) can be obtained on SUAVs that have short duration flights\nwith limited observational periods (i.e., only âË?¼ââ?°Â¤5 minutes of data). This is a significant result for the UAV flight testing community\nbecause an important and relevant benefit of the PPP technique over traditional Differential GPS (DGPS) techniques, such as\nReal-Time Kinematic (RTK), is that there is no requirement for maintaining a short baseline separation to a differential GNSS\nreference station. Because SUAVs are an attractive platform for applications such as aerial surveying, precision agriculture, and\nremote sensing, this paper offers an experimental evaluation of kinematic PPP estimation strategies using SUAV platform data.\nIn particular, an analysis is presented in which the position solutions that are obtained from post processing recorded UAV flight\ndata with various PPP software and strategies are compared to solutions that were obtained using traditional double-differenced\nambiguity fixed carrier-phase Differential GPS (CP-DGPS). This offers valuable insight to assist designers of SUAV navigation\nsystems whose applications require precise positioning....
Technological advances have enabled the development of a number of optical fiber sensing\nmethods over the last few years. The most prevalent optical technique involves the use of fiber\nBragg grating (FBG) sensors. These small, lightweight sensors have many attributes that enable their\nuse for a number of measurement applications. Although much literature is available regarding\nthe use of FBGs for laboratory level testing, few publications in the public domain exist of their\nuse at the operational level. Therefore, this paper gives an overview of the implementation of FBG\nsensors for large scale structures and applications. For demonstration, a case study is presented in\nwhich FBGs were used to determine the deflected wing shape and the out-of-plane loads of a 5.5-m\ncarbon-composite wing of an ultralight aerial vehicle. The in-plane strains from the 780 FBG sensors\nwere used to obtain the out-of-plane loads as well as the wing shape at various load levels. The\ncalculated out-of-plane displacements and loads were within 4.2% of the measured data. This study\ndemonstrates a practical method in which direct measurements are used to obtain critical parameters\nfrom the high distribution of FBG sensors. This procedure can be used to obtain information for\nstructural health monitoring applications to quantify healthy vs. unhealthy structures....
This paper is to present a thermomechanical topology optimization formulation. By designing structures that support specific\nnondesignable domain, optimization is to suppress the stress level in the non designable domain and maintain global stiffness\nsimultaneously. A global stress measure based on ...
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