AEROTECH V: Progressive Aerospace Research

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Authors: H. Mustapha, K.H. Ismail, T.J. Daim, S.F. Jamil
Abstract: Anechoic chambers are widely used in performing EMC measurements according to the established EMC standards. In space area, the elements of EMC measurements such as emission, immunity and susceptibility are critically important to ascertain that all of electrical and electronic components in the satellite body will function correctly without fail, thus ensures the smoothness of satellite operation upon launching into space. Realising this, level of anechoic chamber performance should always be in the optimum state as possible. This paper presents the specific tests that were carried out in the anechoic chamber as to determine the accuracy of its performance. All four types of tests were run in main chamber, control and amplifier room within frequencies range of 10 kHz to 20GHz. The tests will characterize the shielding effectiveness of RF shielded enclosure, the Field Uniformity Area (FUA), Site VSWR and Normalised Site Attenuation (NSA) of anechoic chamber. The basis of the measurement techniques is described and typical test results are discussed. Based on the results, it is concluded that the anechoic chamber is in good condition, ready for testing and capable to produce reliable output.
252
Authors: Alessandro Gardi, Roberto Sabatini, Subramanian Ramasamy
Abstract: In this paper, we investigate an innovative application of Light Detection and Ranging (LIDAR) technology for the aviation-related pollutant measurements. The proposed measurement technique is conceived for high-resolution characterisation in space and time domains of aviation-related pollutant gases. The system performs Integral Path Differential Absorption (IPDA) measurement in a bistatic LIDAR measurement setup. The airborne component consists of a tuneable Near Infrared (NIR) laser emitter installed on an Unmanned Aircraft (UA) and the ground subsystem is composed by a target reference surface (calibrated for reflectance) and a differential transmittance measuring device based on a NIR Camera calibrated for radiance. The specific system implementation for Carbon Dioxide (CO2) measurement is discussed. A preliminary assessment of the error figures associated with the proposed system layout is performed.
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Authors: Muhammad Ayaz, J. Masud
Abstract: he Environmental Control System (ECS) is an important part of any fighter aircraft and has far reaching repercussions in terms of its capability to operate as an effective weapon system under adverse weatherconditions. The aircrew and majority of electronics depend on ECS to keep temperature, pressure and humidity levels within acceptable limits for efficient operation. These limits are explicitly defined in relevant MIL standards MIL-E-18927E(AS) [1] . In order to thoroughly analyze the ECS of under study aircraft [2, 3], Computational Fluid Dynamics (CFD) analysis techniques have been used. CFD techniques offer great flexibility since various conditions can be simulated and analyzed results can be used for required improvements in the system.
263
Authors: Syaril Azrad, Mohammad Fadhil, Farid Kendoul, Kenzo Nonami
Abstract: Localization of Small-Size Unmanned Air Vehicles (UAVs) such as the Quadrotors inGlobal Positioning System (GPS)-denied environment such as indoors has been done using varioustechniques. Most of the experiment indoors that requires localization of UAVs, used cameras or ultrasonicsensors installed indoor or applied indoor environment modification such as patching (InfraRed) IR and visual markers. While these systems have high accuracy for the UAV localization, theyare expensive and have less practicality in real situations. We propose a system consisting of a stereocamera embedded on a quadrotor UAV for indoor localization. The optical flow data from the stereocamera then are fused with attitude and acceleration data from our sensors to get better estimationof the quadrotor location. Using stereo camera capabilities the quadrotor altitude are estimated usingSIFT Feature Stereo Matching are used in addition to the altitude estimation computed using opticalflow. To avoid latency due to computational time, image processing and the quadrotor control areprocessed threads and core allocation.
270
Authors: Aaron Aw Teik Hong, Renuganth Varatharajoo
Abstract: This paper presents a numerical model for a flexible tethered satellite system in both planar and co-planar environment. This tethered satellite system consists of three rigid bodies with two flexible tethers, each connecting two rigid bodies with one located in the center serving as the mothership. The dynamics of the system include tether deformations, rotational dynamics and orbital mechanics. Five different materials that are commonly used will be tested accordingly in order to observe its performance based on the tension of the tether. It is found that, based on all of the materials simulated, diamond has the best tension performance.
281
Authors: Mohd Badrul Salleh, Nurulasikin Mohd Suhadis
Abstract: In this paper, a three-axis attitude control of a small satellite employing control moment gyroscope (CMG) is presented. A four single gimbal control moment gyroscopes (4-SGCMG) cluster has been employed as the actuator and a proportional-derivative (PD) based attitude control approach has been utilized. The singularity robust (SR) steering law has been employed to investigate its capability in avoiding the singularity state of the CMG system with respect to the mission operation by setting the initial gimbal angle further from the singularity state. The presented control law was simulated in the MATLAB® SIMULINK® software. Results obtained from the simulation show the effectiveness of the control algorithm.
286
Authors: Harijono Djojodihardjo, Ali Yousefian
Abstract: Solar sailing has been an attractive concept and possibly an alternative mean of space propulsion for decades to come since solar sail spacecrafts can generate thrust without requiring any propellant. While the resulting acceleration is small, the continuous thrust would lead to high speed.  The present work serves to demonstrate the potential of solar sail by analyzing the dynamics of a spacecraft utilizing solar sail and by carrying out a parametric study for an interplanetary mission exemplified by specific trajectory to Mars.
291
Authors: Karim Kamalaldin, Mohamed Okasha
Abstract:

This paper investigates the design methodology of low Earth inclined circular orbits for remote sensing satellites to satisfy certain mission requirements and constrains such as coverage, resolution, illumination conditions and attitude maneuvers capabilities. Although sun synchronous orbit (SSO) proved to be a good candidate for most remote sensing applications due to its constant lighting conditions and global coverage, low inclined orbits are distinguished by long ground track especially if the target area of concern has horizontal rectangular border. With that respect, low inclined orbits may lead to improvement of the satellite imaging accessibility to the target area per day or reduction of satellite revisit time compared to SSO. This paper exploits these characteristics for low inclined orbits. The target area considered in simulation is between 220 and 320 N latitude lines with 2.5 m ground sample resolution. The satellite maximum rolling capability is 350 and the sun elevation angle is constrained between 300 and 700 for purpose of maximizing the quality of the obtained images. Matlab and STK software are employed to define the initial orbital parameters to meet these conditions for a low inclined orbit.

298
Authors: Subramanian Ramasamy, Manoj Sangam, Roberto Sabatini, Alessandro Gardi
Abstract: The design and trajectory computation algorithms of an innovative Flight Management System (FMS) for Unmanned Reusable Space Vehicle (URSV) are presented. The proposed FMS features a number of common functionalities with modern aircraft FMS that enable flight planning in non-segregated airspace, as well as specific features for optimal trajectory generation and space segment monitoring of the flight mission. The general avionics architecture of URSV is presented and the specific FMS algorithms are developed to cope with the flight vehicle optimal trajectory planning and monitoring. Simulation case studies are performed in a realistic operational scenario resulting in the rapid generation of feasible trajectories, ensuring no violation of the defined mission and vehicle dynamics constraints. Additionally, error budget analysis is performed on longitudinal profile trajectories to evaluate the URSV performance.
304
Authors: Samira Eshghi, Renuganth Varatharajoo
Abstract: Combined Energy and Attitude Control System (CEACS) is an optimization approach that combines the energy storage system and the attitude control system. With a double counter rotating flywheel simultaneously serving as energy storage device and as attitude control actuator, CEACS requires an accurate control strategy to obtain the mission requirements. In addition, it is important to design the control law to be invariant to uncertainties and disturbances, and guarantee robustness as CEACS inherits these in-orbit uncertainties. This paper presents a nonlinear control employing sliding mode to enhance the CEACS attitude control capability. The mathematical model for the conventional and boundary layer sliding mode controls are developed herein for CEACS. The controller provides enhancement in pointing accuracies, reasonable transient responses and a robustness against uncertainties and in-orbit disturbances.
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