This is the accepted version of the paper.This version of the publication may differ from the final published version. Abstract This paper presents a study on the energy exchange taking place on articulated helicopter main rotor blades. The blades are hinged and the flap/lag modes are highly coupled. These dynamical couplings existing between the two degrees of freedom are clearly identifiable as the nonlinear terms that appear in the equations of motion, are key to understand the energy exchange process. The work here conducted is carried out using VehicleSim, a multibody software specialized in modelling mechanical systems composed by rigid bodies. A spring pendulum system is also studied in order to examine its nonlinear behaviour, and to establish existing analogies with the rotor blade nonlinear dynamics. The nonlinear couplings of both systems are compared to each other, and commensurability condition is analysed by means of Short Time Fourier Transform (STFT) methods as well as the flap and lag amplitudes spectrum. Simulations are carried out and the obtained results show clear analogies in the energy exchange process taking place in both systems. The stability of these modes is also studied using Poincare' map method. Permanent repository link

This is the accepted version of the paper.This version of the publication may differ from the final published version. In this paper, an intelligent control approach based on Neuro-Fuzzy systems performance is presented with the objective of counteracting the vibrations that affect the low-cost vision platform onboard an unmanned aerial system of rotating nature. Permanent repository linkA scaled dynamical model of a helicopter is used to simulate vibrations on its fuselage. The impact of these vibrations on the low-cost vision system will be assessed and an intelligent control approach will be derived in order to reduce its detrimental influence.Different trials that consider a Neuro-Fuzzy approach as a fundamental part of an intelligent semi-active control strategy have been carried out. Satisfactory results have been achieved compared to those obtained by means of vibration reduction passive techniques.

This is the accepted version of the paper.This version of the publication may differ from the final published version. Permanent repository link AbstractThis work describes a model developed to analyze the aerodynamic loads on a helicopter model on conventional configuration implemented with VehicleSim, a multibody software specialized in modelling mechanical systems composed by rigid bodies. The rotors are articulated and the main rotor implementation takes into account flap, lag and feather degrees of freedom for each of the equispaced blades as well as their dynamic couplings. This article presents an aerodynamic model that allows to simulate hover, climb, descent and forward flight as well as trajectories under the action of several aerodynamics loads. The aerodynamic model has been built up using blade element theory. All the dynamics, aerodynamic forces and control action are embedded in a single code, being this an advantage as the compilation time is greatly reduced. The software used in this work, VehicleSim does not need external connection to other software. This new tool may be used to develop robust control methods. The nonlinear equations of the system which can be very complex, are obtained, in particular, this article presents the equations for flap and lag degrees of freedom in hover flight. The control approach used in here consists of PID controllers (Proportional, Integral, Derivative), which allow to use VehicleSim command exclusively to simulate several helicopter flight conditions. The results obtained are shown to agree with the expected behaviour.

The analysis of the nature and damping of unwanted vibrations on Unmanned Aerial Vehicle (UAV) helicopters are important tasks when images from on‐board vision systems are to be obtained. In this article, the authors model a UAV system, generate a range of vibrations originating in the main rotor and design a control methodology in order to damp these vibrations. The UAV is modelled using VehicleSim, the vibrations that appear on the fuselage are analysed to study their effects on the on‐board vision system by using Simmechanics software. Following this, the authors present a control method based on an Adaptive Neuro‐Fuzzy Inference System (ANFIS) to achieve satisfactory damping results over the vision system on board

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