Control of approach and landing phase for reentry vehicle using fuzzy logic

The reentry vehicle is affected by various disturbances such as a wind gust, atmospheric condition or aerodynamic problems in the approach and landing phase. Therefore it is necessary to design a robust control scheme. This paper presents a control scheme using Mamdani fuzzy PD controller. In this paper, the reference trajectories are generated using geometric parameters for disturbed circumstances with 4 cases: nominal, headwind and tailwind, drag increased case. Then, a Mamdani fuzzy PD controller was designed in this study. Twenty-five rules were applied in the knowledge-based system. The max–min method for a fuzzy inference system and the center-of-mass method in defuzzification were used. Finally, guidance and control simulations are performed for verification of proposed controller using generated reference trajectories. In addition, the Monte Carlo simulation is performed considering various disturbances. The results show that proposed Mamdani fuzzy PD controller has reliability and robustness for control of reentry vehicle with wind disturbance in the approach and landing phases.     

Visualization and PIV study of wing-tip vortices for three different tip configurations

The planform, profile, and cross-sectional views of the wing-tip region of a half-wing model with an aspect ratio of 3.2 and three different wing configurations, namely, square-cut, simple fairing, and Whitcomb?s full winglet wing-tip, were visualized at various angles of attack using smoke-wire visualization technique. Visualization pictures clearly show that the wing-tip vortices at different angles of attack and wing-tip configurations had distinct formation and structure characteristics. A comparison of simple fairing and Whitcomb?s winglet configurations shows that the wing-tip vortices of the Whitcomb?s winglet configuration were reduced in strength and displaced outboard and upward, at least in the near-wake region. This resulted in an increased lift-to-drag ratio for the Whitcomb?s winglet configuration. The changes in the wing-tip vortex characteristics and the improved aerodynamic performance of the winglet were confirmed by Particle Image Velocimetry (PIV) measurements of the cross-flow velocity of the wing-tip trailing regions and the force measurement of the model.     

Genesis and preservation of a uranium-rich paleozoic epithermal system with a surface expression (Northern Flinders Ranges, South Australia): radiogenic heat driving regional hydrothermal circulation over geological timescales

The surface expressions of hydrothermal systems are prime targets for astrobiological exploration, and fossil systems on Earth provide an analogue to guide this endeavor. The Paleozoic Mt. Gee-Mt. Painter system (MGPS) in the Northern Flinders Ranges of South Australia is exceptionally well preserved and displays both a subsurface quartz sinter (boiling horizon) and remnants of aerial sinter pools that lie in near-original position. The energy source for the MGPS is not related to volcanism but to radiogenic heat produced by U-Th-K-rich host rocks. This radiogenic heat source drove hydrothermal circulation over a long period of time (hundreds of millions of years, from Permian to present), with peaks in hydrothermal activity during periods of uplift and high water supply. This process is reflected by ongoing hot spring activity along a nearby fault. The exceptional preservation of the MGPS resulted from the lack of proximal volcanism, coupled with tectonics driven by an oscillating far-field stress that resulted in episodic basement uplift. Hydrothermal activity caused the remobilization of U and rare earth elements (REE) in host rocks into (sub)economic concentrations. Radiogenic-heat-driven systems are attractive analogues for environments that can sustain life over geological times; the MGPS preserves evidence of episodic fluid flow for the past ～300 million years. During periods of reduced hydrothermal activity (e.g., limited water supply, quiet tectonics), radiolytic H(2) production has the potential to support an ecosystem indefinitely. Remote exploration for deposits similar to those at the MGPS systems can be achieved by combining hyperspectral and gamma-ray spectroscopy.     

Efficient scheduling algorithm for demand-assigned TDMA satellitesystems

An efficient scheduling algorithm (stations burst plan) for demand-assigned time-division multiple-access (TDMA) satellite network systems is introduced. The total demand for transmitting data through a transponder may exceed the available bit-rate capacity, and a scheduler of the system wishes to utilize the system with minimum changes of slot allocations while maximizing throughputs. By implementing such a burst-plan algorithm, transmission of all demanded data traffic can be completed with minimum unused resources (idle slots). The underlying ideas adopted for the algorithm are that jobs with shorter remaining processing times should have higher priorities and that as many jobs are processed at a time as possible. The algorithm is particularly useful for deriving smooth burst plans for a satellite system with a large number of ground stations     

A passive tracking filter for missile capture

A practical filter is suggested for ground-based missile tracking in a capture-guidance mode utilizing angle-only measurements from a passive missile sensor, and its performance is evaluated by a realistic system-simulation study. A missile-acceleration model that provides inputs to the filter is also suggested. The filter has a decoupled structure of independent azimuth and elevation channels, which requires fewer computations in solving the filter gain compared to a coupled structure. Simulation results show good tracking performance of the filter when used in association with the proposed missile-acceleration model     

Procedure and methodologies for managing the risk of space object reentry

This paper proposes a procedure for managing the risk of reentering space objects and risk assessment methodologies used for the process. The proposed procedure comprises three phases encompassing the whole reentry stages of space objects. Mathematical models for assessing the impact risk of the reentering space objects by utilizing the information available during different risk management phases and the recommended risk analysis results for public communication are presented. The concept of the conditional casualty expectation is proposed as the metric representing the reentry risk and the method to compute its profile is introduced. A case study on the risk management procedure with the dataset on an actual reentry event is conducted to demonstrate the efficacy of the proposed procedure.     

Soldier Identification System utilizing low probability ofintercept (LPI) techniques

This paper documents the design of a laser/radio frequency (RF) Soldier Identification (ID) System developed by Dynetics, Inc., Harris, Corp., and the US Army Communications and Electronics Command (CECOM). The Soldier ID system includes an Interrogation Unit with a programmable activation code. The Interrogation Unit consists of a directive, eye-safe laser and a spread-spectrum RF transceiver. This allows for a low probability of intercept (LPI) interrogation, which is of interest during covert operations. A Responder Unit is worn, for example, by a soldier and transmits an LPI spread-spectrum RF response, only after receiving the proper interrogation codes. The basic subsystems for the identification system are a Laser Interrogation Unit, an RF Responder Unit, and an electronic Programming Unit. The operating principles for the subsystem are reviewed, and the design issues are discussed. In addition to the preliminary design performed under Phase I of the program, a breadboard system was developed to validate the proof-of-principle concept. Hardware implementation is reviewed and test results are presented. The brassboard development and engineering plans are also presented     

A high-order SPH method by introducing inverse kernels

The smoothed particle hydrodynamics (SPH) method is usually expected to be an effi-cient numerical tool for calculating the fluid-structure interactions in compressors; however, an endogenetic restriction is the problem of low-order consistency. A high-order SPH method by intro-ducing inverse kernels, which is quite easy to be implemented but efficient, is proposed for solving this restriction. The basic inverse method and the special treatment near boundary are introduced with also the discussion of the combination of the Least-Square (LS) and Moving-Least-Square (MLS) methods. Then detailed analysis in spectral space is presented for people to better under-stand this method. Finally we show three test examples to verify the method behavior.     

Proportional fuzzy feed-forward architecture control validation by wind tunnel tests of a morphing wing

In aircraft wing design, engineers aim to provide the best possible aerodynamic performance under cruise flight conditions in terms of lift-to-drag ratio. Conventional control sur-faces such as flaps, ailerons, variable wing sweep and spoilers are used to trim the aircraft for other flight conditions. The appearance of the morphing wing concept launched a new challenge in the area of overall wing and aircraft performance improvement during different flight segments by locally altering the flow over the aircraft's wings. This paper describes the development and appli-cation of a control system for an actuation mechanism integrated in a new morphing wing structure. The controlled actuation system includes four similar miniature electromechanical actuators dis-posed in two parallel actuation lines. The experimental model of the morphing wing is based on a full-scale portion of an aircraft wing, which is equipped with an aileron. The upper surface of the wing is a flexible one, being closed to the wing tip; the flexible skin is made of light composite materials. The four actuators are controlled in unison to change the flexible upper surface to improve the flow quality on the upper surface by delaying or advancing the transition point from laminar to turbulent regime. The actuators transform the torque into vertical forces. Their bases are fixed on the wing ribs and their top link arms are attached to supporting plates fixed onto the flex-ible skin with screws. The actuators push or pull the flexible skin using the necessary torque until the desired vertical displacement of each actuator is achieved. The four vertical displacements of the actuators, correlated with the new shape of the wing, are provided by a database obtained through a preliminary aerodynamic optimization for specific flight conditions. The control system is designed to control the positions of the actuators in real time in order to obtain and to maintain the desired shape of the wing for a specified flight condition. The feasibility and effectiveness of the developed control system by use of a proportional fuzzy feed-forward methodology are demon-strated experimentally through bench and wind tunnel tests of the morphing wing model.     

Cr12MoV钢电火花辅助铣削实验研究

以典型难切削金属材料Cr12MoV模具钢为研究对象，使用ABAQUS对其在电火花放电条件下温度场进行数值模拟，在不同进给率下对其进行传统铣削和电火花辅助铣削对比试验。借助高速摄像机、扫描电镜和测力计等设备，对其切削力特征、表面形貌和刀具磨损进行了对比分析研究。结果表明，电火花辅助铣削的切削力比传统铣削降低28.57%~51.47%，表面粗糙度降低2/3。与传统铣削相比，电火花辅助铣削在降低切削力、提高表面质量和减少刀具磨损方面具有显著优势。