IRANIAN JOURNAL OF MECHANICAL ENGINEERING (ENGLISH)
Year:2016 | Volume:18 | Issue:1|Papers Count:7

In this paper, we investigate the problem of model predictive control of pitch angle of a flexible launch vehicle using neural networks. We simulate motion of launch vehicle on the pitch plane by considering effects of flexibility. Aeroelstic effects are also modeled by adding elastic terms of the structure to state space control equations which completes the vehicle model. To control the vehicle, we use a model predictive controller which is based on a neural network. Basic notions of this controlling approach are presented and we explain how a neural network can be used for this purpose. Experimental results on synthetic data in Simulink environment demonstrates our approach is useful and effective and neural networks can be used to control a vehicle in a nonlinear, adaptive control setting.

The large amplitude free vibration behaviour of an Euler-Bernoulli beam with immovable ends subjected to the thermal loads is investigated. Applying the Hamilton’s principle, the beam governing equation of motion is derived. By implementing the Galerkin’s method, the ordinary nonlinear differential equation is derived and because of the large coefficient of the nonlinear term, the Homotopy Perturbation Method (HPM) is used to solve the governing nonlinear equation and the accuracy of the mentioned method is investigated. The results are validated by comparing them with those available in the literature. Moreover, the effects of the system parameters including foundation coefficients, thermal load and vibrational modes on the system nonlinear vibration behaviour are investigated.

In this study a frequency analysis of a sandwich plate with multilayered composite face-sheets and flexible core under thermal conditions is investigated for different boundary conditions. In this regard, thermal effects and temperature dependent properties of the core are considered. In this study, for driving the equations of motion, a hybrid LW/ESL finite element formulation, considering the thermal effects is proposed by which the number of unknowns is independent on the number of layers. This new formulation is in the framework of Carrera’s Unified Formulation (CUF). The CUF unify many theories in a unified form which can be differed by the order of expansion and definition of the variables in the thickness direction. In order to satisfy the interlaminar continuity of transverse stresses between the layers the Reissner Mixed Variational Theorem (RMVT) is employed. In this research for considering the thermal effects, the nonlinear strains are used. Results of this formulation are compared with available results which show the high accuracy with low computational cost of the proposed formulation. Results show that with increasing the temperature, the frequency of structure decreases significantly, due to the degradation of the properties of the core. In this study, some new results are presented for different thermal conditions and also different boundary conditions.

the increasing importance of the need for electricity and the need to have a healthy and pollution-free environment have prompted researchers to constantly track renewable sources of energy such as wind, solar, geothermal and so on instead of fossil fuels. But technology is not advanced enough yet to utilize them, and the costs associated with setting up and implementing them is not reasonable. In order to find and complement new methods to employ renewable energy, this paper investigates a new generator, i.e., Kite-Gen. The idea first explored in Torino, Italy, and is now being studied around the world. One of the most important factors to produce the maximum energy in a specific Kite-Gen, is to control its direction in a correct way. The purpose of this paper is to find a feedback control and to obtain proper eigenvalues for zero steady-state error.

The effect of strain hardening modulus on axisymmetric buckling of circular cylindrical shells made of aluminum and steel materials is investigated, so the nonlinear dynamic equations of cylindrical shells with different strain hardening modulus for cylindrical shells made of aluminum material and different linear and multi-linear strain hardening modulus for cylindrical shells made of steel material are solved for three types of boundary conditions and two types of loading. It is found that under investigated conditions, changing of strain hardening modulus for cylindrical shells made of aluminum and steel materials transmit the buckling shape from plastic buckling to progressive buckling.