Search

M ulti wind t U rbine S imulation T ool (MUST) is a new CENER's in-house code, based on NREL's OpenFAST code, designed to allow the aero-hydro-servo-elastic modelling of novel multi-rotor wind turbine concepts. MUST also includes a new aerodynamic module, called AeroVIEW (Aero dynamic V ortex f I lam E nt W ake) based on an implementation of the Free Vortex filament Method (FVM) combined with an unsteady Lifting Line (LL). This model allows to represent the influence existing between all the rotors, in each one of them. In this article, a validation of AeroVIEW performance for single and multi-rotor configurations is presented. First, a study of the wake properties (wake geometry, core radius and circulation of tip vortex filament) obtained with AeroVIEW has been successfully compared with several MexNext III cases. Then, an analysis of the rotor wakes interaction, in different arrays of wind turbines, has been made, obtaining power and thrust increases, due to this rotor-wake interaction, for different conditions. The increases obtained in power are very similar to results of high fidelity tools found in the literature. Moreover, this beneficial effect on the power generated, has a counterpart in the average thrust, whose increase is around half of the power production increase. • MUST is a new CENER aeroelastic tool to simulate multi-rotor wind turbines. • MUST includes AeroVIEW a FVM based module usable for single or multi-rotor turbines. • AeroVIEW captures with reliability key aspects of multi-rotor turbines. • The power benefit of multi-rotors has a counterpart in lower effect on thrust. • AeroVIEW has an acceptable computational cost. [ABSTRACT FROM AUTHOR]

In this article, we introduce a translational force control method with disturbance observer (DOB)-based force disturbance cancellation for precise 3-D acceleration control of a multi-rotor unmanned aerial vehicle (UAV). The acceleration control of the multi-rotor requires conversion of the desired acceleration signal to the desired roll, pitch, and total thrust. However, because the attitude dynamics and the thrust dynamics are different, simple kinematic signal conversion without consideration of those difference can cause serious performance degradation in acceleration tracking. Unlike most existing translational force control techniques that are based on such simple inversion, our new method allows controlling the acceleration of the multi-rotor more precisely by considering the dynamics of the multi-rotor during the kinematic inversion. By combining the DOB with the translational force system that includes the improved conversion technique, we achieve robustness with respect to the external force disturbances that hinder the accurate acceleration control. $\mu $ -analysis is performed to ensure the robust stability of the overall closed-loop system, considering the combined effect of various possible model uncertainties. Both simulation and experiment are conducted to validate the proposed technique, which confirms the satisfactory performance to track the desired acceleration of the multi-rotor. Note to Practitioners—This article presents a method for controlling the acceleration of a multi-rotor accurately under the presence of translational force disturbance. Unlike the existing methods, the new signal conversion technique that considers the dynamics of the multi-rotor in the process of converting the target translational acceleration signal to the target roll, pitch, and thrust signal enables a more accurate translational force control. The DOB structure applied to the translational force control system overcomes the acceleration control performance deterioration caused by external translational force disturbance. Through the combination of the two techniques, the acceleration of the multi-rotor can be accurately controlled not only in the nominal environment but also in the presence of translational force disturbance. [ABSTRACT FROM AUTHOR]

The propulsion system of a multi-rotor UAV plays a fundamental role in the aircraft flight characteristics. In fact, it generally represents the major contributor to the aerodynamic forces acting on the vehicle. While several approaches for modeling rotor thrust and drag forces exist, the problem of identifying the parameters for these models is still challenging. In this paper we propose a systematic method for identifying a limited number of parameters which guarantee accurate thrust and drag prediction according to Blade Element Theory (BET). Simple experimental tests employing a popular rotor system and a custom-made quadrotor are used both in the identification phase and for the final validation. The discussion of the results illustrates the accuracy of the method, while highlighting the modeling limit of BET. A refinement using Blade Element Momentum Theory is proposed and validated with the support of experimental data. [ABSTRACT FROM AUTHOR]