سال:1392 | دوره: | شماره: |تعداد مقالات:6

The main goal of this article is to implement the MSG-3 process in structure field for an SSI component of b747 aircraft. This process is expected to increase the ease of aircraft maintenance and its safety level. MSG-3 logic took a top-down or consequence of failure approach meaning that MSG-3 reduces the maintenance cost and upgrades safety. Moreover, it can significantly help saving the time and providing financial benefits for the design approach and the development of maintenance programing. In this study, in correspondence with the SLD of MSG-3, an SSI component is selected and its fatigue crack growth analysis is investigated. The approach of this study is to use the FEM and fractography for the purpose of exploring the loading.

This paper is concerned with the statistical model development issues, necessary for rapid estimation of the rotor sizing for single main rotor helicopters at the preliminary design stage. However, Central Composite Design (CCD) method, simulation-based data collection, linear regression analysis, mathematical modelsdevelopmentand validations through the analysis of variance (ANOVA) were performed as central themes in this approach. The CCD enforced the use of replicated central points and some star points, added to the basic factorial design space, required for constructing the test plan matrix. This matrix was used to developed mathematical models in the form of quadratic polynomials (second-order), that represented the physical size of rotor as functions of the helicopter gross weight, maximum forward flight speed, main and tail rotor blade number and their interactions. The validations were examined by ANOVA and comparing against data for a general single rotor configuration. Using this approach, improvements in physical sizing of both main and tail rotor of the single rotor were obtained using minimum number of data, provided by CCD test plan. The obtained results of this work support the ongoing researches for the development of rapid prototyping, especially, main and tail rotor sizing of helicopters.

A pressure based implicit procedure to solve the Euler and Navier-Stokes equations is developed to predict transonic viscous and inviscid flows around the pitching and heaving airfoils with a high resolution scheme. In this process, no northogonal and non moving mesh with collocated finite volume formulation are used. In order to simulate pitching or heaving airfoil, oscillation of flow boundary condition is applied. The boundedness criteria for this procedure are determined from Normalized Variable Diagram (NVD) scheme. The procedure incorporates the k- e eddy-viscosity turbulence model. This process is tested for inviscid and turbulent transonic aerodynamic flows around oscillation airfoil. The results are compared with other existing numerical solutions and with the experimental data. The comparisons show that the resolution quality of the developed algorithm is significant.

In this paper, with the aim of estimating internal dynamics matrix of a gimbaled Inertial Navigation System (as a discrete linear system), the discrete-time Hamilton- Jacobi-Bellman (HJB) equation for optimal control has been extracted. Heuristic Dynamic Programming algorithm (HDP) for solving the equation has been presented and then a neural network approximation for cost function and control input has been extracted to simplify the solutionof HJB. Design process of the optimal controller shows that, we do not need to know the system matrix. This important issue and the convergence of the HDP algorithm to the optimal control policy makes possible the estimation of the internal dynamics matrix.

An advanced guidance law is developed for reentry phase of a reentry vehicle. It can achieve small miss distance and desired impact attitude angle, simultaneously. To meet this requirement, a guidance law based on the fuzzy logic control approach is developed. It is partitioned into three stages. This guidance law does not require linearization of missile engagement model. Line-of-sight angle and flight path angle are used to constitute the rule antecedent of the guidance law to shape an appropriate flight trajectory for engagement. Numerical simulation results and comparison with an existing algorithm demonstrated that the proposed guidance law offers satisfactory performance and robustness, fulfilling its design goals.

A new procedure for deriving nonlinear mathematical modeling for a specific class of aerospace hydro-mechanical control valves is presented. The effects of friction on the dynamic behavior of these types of valves along with the experimental verifications are also given. The modeling approach is based on the combination of the following three tasks: decomposition of the valve into simple specific subsystems; derivation of the governing equations of each subsystem; and determination of the unknown parameters and coefficients using dynamic and static tests. Dynamic analysis shows that the presence of friction causes the hysteresis phenomenon in these valves and friction force increment causes an increase in the tracking error. On the other hand, excessive reduction of the friction force causes an instable performance. Therefore, a trade-off between the amount of tracking error and stability margins must be considered.