Masoud Alizadeh, Mehrdad Ebrahimi Dormiani, Mahdi Noori Dabir,
Volume 17, Issue 6 (8-2017)
Abstract
This paper investigates the Tri-Tilt Rotor VTOL UAV. The aim of this study is to represent a comprehensive dynamic model, eleven degree of freedom at six flight phases (hover, descend, climb, forward, transient and cruise) and control the vehicle to reach best flight condition. For this purpose, the vehicle equations of motion are derived in tensor form and have been expanded in the coordinate systems, based on multi-body (vehicle and three electric motors) modeling approach in order to consideration of motors gyroscope effects on flight dynamic. Depending on vehicle flight phase, propulsion and aerodynamic forces and moments are determined separately. Blade Element Momentum Theory (BEMT) is used to obtain motors propulsion forces and moments at hover, descend, climb and forward phases. After that, with utilizing of controller for each channel flight, the trim condition is calculated and then for the sake of linearization using analytical method, dynamic and control matrixes are derived. This calculated model is qualified as linear model in order to design the model predictive and adaptive controller. For climb phase, as the nonlinear model receding from linear model, the linear model predictive controller performance was diminishing whereas the function of model reference adaptive control in spite of the uncertainties was better.
Seyyed Mohammad Sajad Seifi, Mohammad Mojaddam, Pouyan Hashemi Tari,
Volume 18, Issue 9 (12-2018)
Abstract
Aerodynamic and optimal design of a blade of a horizontal axis wind turbine (HAWT) has been performed in order to extract maximum power output with considering the strength of the blade structure resulted from different loads and moments. A design procedure is developed based on the Blade Element Momentum (BEM) theory and suitable correction factors are implemented to include three-dimensionality effects on the turbine performance. The design process has been modified to achieve the maximum power by searching an optimal chord distribution along the blade. Based on the aerodynamic design, the blade loads have been extracted and the blade mechanical strength has been investigated by analyzing the thickness of the blade surface and the blade material. The developed numerical model can be considered as a suitable tool for aerodynamically and mechanically design of a turbine blade. The results for a 500 W turbine show that the turbine performance improves by 5% approximately, by modifying chord radial distribution. Yield stress analysis shows the effect of introduced chord distribution on the blade strength, in different blade thicknesses and different blade materials. In addition, optimum tip speed ratio for having favorable mechanical safety factor is derived. Three different airfoil are examined for this investigation and comparing their mechanical safety factor.