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International Review of Aerospace Engineering - August 2009 - Papers

A Method for Real-Time Task Assignment and Path Planning for Multiple UAVs Considering Obstacle Avoidance
Aeroelastic Analysis for Eagle 150b Aircraft Wing
Model-Based Actuator Fault Tolerant Robust Control Architecture: an Unmanned Aerial Vehicle Example
Development of 10DOF Nonlinear Model of an Autonomous Helicopter with Control Rotor System
A Triangular Plate and Shell Element for the Force Method
Turnaround Performance Evaluation for Optimal Time Buffering
Flutter of Perforated Metallic Plates Reinforced with Segmented Piezoelectric Patches
Effect of Initial Shape Imperfection/Cutout on Buckling of Composite Cylindrical Shells

International Review of Aerospace Engineering - Papers

A Method for Real-Time Task Assignment and Path Planning for Multiple UAVs Considering Obstacle Avoidance
by Shin-Ichiro Higashino, Toshihiro Takebayashi

Vol. 2. n. 4, pp. 175-184

Abstract - This paper presents a quick method using Evolutionary Computation for simultaneous optimization of task assignment and path planning for multiple UAVs considering obstacle avoidance. The method proposed for the optimization of task assignment is named Radial Segmentation Task Assignment (RSTA) method which uses Evolutionary Computation based on the results of distributed path planning optimization, and the method for path planning is named Evolutionary Computation and Simplified Rule-Based (EC-SRB) hybrid method of which feature is that the obstacle avoidance using rule-based method and the optimization of the combination of the legs which has already avoided obstacles are separated. Calculation speed of the proposed method has been measured using a developed real-time simulator, and the results show that the task assign and path planning problem can be optimized within approximately 5 seconds with 31 waypoints and 3 usable UAVs considering terrain and other obstacles. The dependency of the calculation speed on number of waypoints and usable UAVs is also examined, and the calculation speed is proved to be high enough to be used in real time.

Keywords: Task Assignment, Path Planning, Multiple UAVs, Evolutionary Computation, Real-time.

Aeroelastic Analysis for Eagle 150b Aircraft Wing
by A. S. Mohd Rafie, S. Basri, R. Varatharajoo, D. L. Majid, A. H. Mohamed Ariff

Vol. 2. n. 4, pp. 185-191

Abstract - The aim of this paper is to predict the flutter speed of an Eagle 150B aircraft wing by performing a thorough and comprehensive aeroelasticity analysis using computational techniques. There are two types of analysis conducted in this work, namely the actual wing analysis and the wing model analysis. The flutter analysis is performed using the PK-method option in the MSC Nastran and Patran software, where by eigenvalue and eigenvector are computed to determine the stability of the combined structural and aerodynamic system. Both modeling techniques show a good agreement with the experimental technique results. The results also show that the computational technique for actual wing analysis give a better prediction of flutter condition compared to wing model analysis.

Keywords: Computational analysis, Actual Wing Analysis, Wing Model Analysis, Eagle 150B aircraft wing and flutter.

Model-Based Actuator Fault Tolerant Robust Control Architecture: an Unmanned Aerial Vehicle Example
by Sanjay Jayaram

Vol. 2. n. 4, pp. 192-198

Abstract - In this paper, development of a fault tolerant control architecture that couples techniques for fault detection and identification with reconfigurable flight control to augment the reliability and autonomy of an Unmanned Aerial Vehicle (UAV) is presented. The developed fault tolerant control is applied to a fixed wing UAV. The fault tolerant control architecture recovers the UAV performance after the occurrence of faults. Robust measures are developed to identify faulty actuators that would degrade the performance envelopes. These robust measures are in-turn used to design a robust fault tolerant control law which is capable of switching from nominal control law to robust control laws under faulty conditions. It will be shown through simulations that the robust control law is capable of switching to redundant back-ups, thus maintaining the stability and overall performance measures of the system when there is an actuator failure of any kind.

Keywords: Fixed Wing UAV, Robust Measures, Fault Tolerant Control, Actuator Fault Detection, Reconfiguration.

Development of 10DOF Nonlinear Model of an Autonomous Helicopter with Control Rotor System
by Abolfazl Mokhtari, Amir Ali Nikkhah, Alireza Novinzadeh

Vol. 2. n. 4, pp. 199-207

Abstract - Development of the nonlinear 10DOF simulation procedure for a miniature unmanned helicopter is presented in this study. Due to this matter of fact that each blade of rotor has had its own degrees of freedom, the previous studies of the dynamic response of a helicopter yielded to some complications. The most important different between the unmanned model helicopter and the full sized one is summarized into the method of pilot command transmission to the main rotor. Indeed, in the small size helicopter there is the control rotor system which without considering it, modeling of the main rotor dynamics will be impossible. The main novelty of this study is to employ a new analytic method in modeling the main rotor and control rotor dynamic systems. After deriving the model, the 10 DOF nonlinear simulations for a specific model helicopter is performed in the Matlab-Simulink environment.

Keywords: Unmanned Helicopter, Control rotor, 10DOF Modeling, Nonlinear simulation.

A Triangular Plate and Shell Element for the Force Method
by Lazarus Teneketzis Tenek

Vol. 2. n. 4, pp. 208-218

Abstract - Using Complementary Work and the Force Method a triangular element is developed for the analysis of plates and shells. The triangular element has 3 nodes and as nodal unknowns the 3 forces and 3 moments of each node in local/global coordinate systems. A stress plate and shell theory is developed based on integral and variational arguments which yields in its discrete form using matrix methods the global nodal forces and moments. The Force matrix of the element is established and force equilibrium postulated. The theory accepts applied displacements and rotations but applied loads or moments can be inserted as boundary conditions. The solution of the linear system of equations provide the internal loads. After solution, the displacement/rotation field originating from the internal loads can be estimated on an element basis. The force method can provide the distribution of forces/moments inside a structure from external loading. Numerical examples on plates and shells are provided.

Keywords: Complementary Work, Force Method EFM, triangular element, force matrix, plates/shells.

Turnaround Performance Evaluation for Optimal Time Buffering
by Hartmut Fricke, Michael Schultz

Vol. 2. n. 4, pp. 219-229

Abstract - During 2007, 19% of all European flights were more than 15 min late. One contributor to this delay is the insufficient ground operation performance inducing excessive process durations. Whenever these processes are part of the critical Turnaround (TA) path, such as de-boarding, fuelling, cleaning, catering and boarding, the effects immediately propagate an accumulating delay through the ATM network. Recent studies have investigated into the effects of technical aircraft deficiencies onto TA reliability, and could show that significant potential is given for improvement. Field analyses at German airlines showed that pre-set quality standards for punctuality can actually not be met. This paper extends that analysis by considering the individual inbound delay measured at the gate, revealing the correlation between TA process duration and stability versus a given delay with an analytical model. The concept of dynamically scheduling buffer times to compensate for potential delays into the ground time of aircraft turnaround operations is introduced into our model. It can be shown that dynamic buffering may overcome deficiencies of the currently applied buffer strategies for ground processes. The paper closes with a strategy on how to scale gate time to cope with demanding punctuality requirements from the customer’s side. With regards to Airport CDM concepts, the dependencies found may be used in decision support tools to trigger ground handling resource (personnel and tools) planner and motivate for strategies specifically for Ground Handling Companies.

Keywords: Turnaround, Delay Propagation, Critical Path, Ground Handling Operations, Monte Carlo Simulation.

Flutter of Perforated Metallic Plates Reinforced with Segmented Piezoelectric Patches
by A. Amin Yazdi, J. Rezaeepazhand

Vol. 2. n. 4, pp. 230-234

Abstract - The performance of segmented piezoelectric actuator in controlling the flutter of a damaged metallic plate is presented in this study. Numerical studies using commercial finite element software were conducted to investigate the effect of different parameters such as configuration, mass and voltage of segmented piezoelectric patches on flutter velocity of the repaired plate. The main goal of this study is to investigate the application of piezoelectric actuator to repair the metallic plate with square central cutout. Such study is important since it provides the necessary design information for flutter behavior of repaired perforated plates. Particular emphasis is placed on the flutter analysis of a square aluminum plate. Four different configurations for piezoelectric patches are considered. Both symmetric and un-symmetric patches are considered. The result presented here indicated that, the configuration in which, four piezoelectric patches are placed in a cross shape is more effective than the other configurations in increasing the flutter velocity.

Keywords: Panel Flutter, Perforated Plate, Piezoelectric Actuator, Repaired Plate, Patches.

Effect of Initial Shape Imperfection/Cutout on Buckling of Composite Cylindrical Shells
by A. Havasi, J. Rezaeepazhand, A. Khorsand

Vol. 2. n. 4, pp. 235-239

Abstract - Thin-walled shells have wide applications as primary structural elements in simple and complex lightweight structures. In these applications, cylindrical shells contain several imperfections and material discontinuity, namely variously shaped cutout. The understanding of the effects of initial geometric imperfection and cutout on the buckling behavior of such shells is very important. A finite element analysis, using commercial finite element software, is used to study the buckling behavior of cylindrical shells with imperfection or circular cutouts. Particular emphasis is placed on circular cylindrical shells subjected to an axial compression load. Both perfect shells with cutouts and shells with initial geometric imperfection are considered. The main objective of this study is to investigate the buckling behavior of laminated composite shells with circular cutouts and initial geometric imperfection. The effect of cutout geometry and size, material properties, fiber angle, stacking sequences, and initial geometric imperfection are discussed. The results presented herein indicated that, buckling response of laminated composite shells is significantly changed by cutout size, fiber orientation, stacking sequences, and amplitude of initial geometric imperfections.

Keywords: Cylindrical shells, Cutout, Buckling, Shape Imperfection, Sublaminate.