ERF European Rotorcraft Forum
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A Kalman-based identification approach for distributed aerodynamic loads on a rotating blade
No full textThe rotating blades of the helicopter are constantly interacting with the external fluid generating vibratory loads. These excitations are then transmitted to the rotor hub and can lead to failures in the main rotor system. The knowledge or prediction of the aerodynamic loads become thus of great importance for design and failure prevention. Several experiment-based and model-based techniques have been presented in literature, but given the complexity in helicopter modelling, high accuracy can only be reached if a large amount of sensor data and/or a high-fidelity numerical model is available. This contribution focuses on the usage of the Kalman filtering technique for rotor load estimation. The filter presents two main advantages: i) usage of a minimum set of sensors; ii) compensation of a low-fidelity model by accounting for sensor and model uncertainties. The problem of state and load estimation is addressed in this paper on a rotating helicopter blade through a numerical example. Numerical results show an accurate state reconstruction with respect to the selected sensor layout and model uncertainties. The distributed aerodynamic loads can be accurately reconstructed in post-processing
Particle tracking analysis of a rotor in ground effect
Get PDFIn the present work, computational fluid dynamics (CFD) is used to predict the behavior of ground particles, uplifted by a two-bladed rotor. The paper focuses on defining a safety area where the presence of particles can be considered as negligible, and compare this area with other distance based criteria. Using data of three different aircraft, scaling factors have been used to take into account the different size of the small-rotor studied and real case scenarios. The results show how heavier helicopters may generate the most dangerous situations, in terms of presence of particles in a delimited area
Modelling, simulation and dynamics of a synch-rotor aircraft
Get PDFThis paper presents a detailed modelling, control system design, and numerical simulation of a rotary wing aircraft with two synchronised rotors. Following the derivation of the complete non-linear 6 DoF equations, a nested loop control architecture made of attitude stabilisation and trajectory tracking is designed after a linearisation process. Numerical simulation and performance analysis are carried out. Results concerning hovering and forward flight, relevant from the perspective of practical applications are presented and discussed. The synch-rotor configuration appears suitable and effective for application where Unmanned Aerial Systems are foreseen such as environment monitoring, aerial photogrammetry, and load transportation
Rotor parameters of small weight helicopters
Get PDFIn recent years, a significant number of one and two-seats small weighted helicopters have appeared. This fact makes it possible to analyse the parameters and determine the parameter dependencies for this helicopters class. Knowledge of such dependencies is necessary for the preliminary design stage. The analysis performed in this paper and the comparison of it with the statistical data of all the categories of helicopters made it possible to determine the necessary corrections in the methods for design the parameters of the little helicopter's rotor systems
Full-envelope flight control for a multi-rotor Cessna-182 eVTOL
Get PDFThis paper considers the flight control for an electric Vertical Take-Off and Landing vehicle, whose configuration is based on the fixed-wing Cessna 182 mounted with additional 4 tilting rotors to provide helicopter flight characteristics. Consequently, 2 flight modes are identified for this vehicle: helicopter mode and airplane mode. For the purposes of simple tuning and easy implementation, we exploit Proportional-Integral-Derivative methods in each flight mode for the control law design. The transition between the 2 modes are controlled based on a feedforward gain scheduling technique, which is typical for tiltrotor configurations. The performances of the controllers are first examined on the simplified/linearised models before they are tested on the nonlinear one, which leads to increased confidence in practice. The simulation results show that the control outcome is successful, in the sense that the vehicle can stabilise and provide fast tracking in each mode. Moreover, no significant changes in the flight properties are observed during the transition period
Hybrid solver for aerodynamic design
No full textThe low-fidelity generalized inverse solver is developed. It allows to control the pitching moment when the original pressure distribution is corrected. The new hybrid method of aerodynamic design is stated. It uses the generalized inverse solver as a geometry parameterizer along with the solvers of any fidelity to evaluate the objective functio
The modernization of civil rotorcraft certification system in Korea
Get PDFThe ROK MND have successfully developed two types of military helicopters in last two decades, in cooperation with Airbus Helicopters. Though these rotorcrafts were basically developed to conduct various tactical duties, their civil derivatives were also developed for cost-effective operation. Since it is apparent that these rotorcrafts will apply for their STC and RTC respectively, the demand to harmonize the civilian rotorcraft certification system was clearly recognized in ROK. Therefore, the KIAST (Korea Institute of Aviation Safety Technology) have been conducting a project since 2017, to improve the civil rotorcraft certification system. This document is providing the general overview of this effort
Design issues of dynamics of helicopter main rotor blades under the influence of wind in the parking lot
Get PDFThe paper addresses the issue of designing helicopter main rotor blades exposed to wind in the parking lot. Necessary wind conditions have been determined to be taken into account when designing the blades. In addition, it shows a method for calculating dynamic stresses in a moored and non-moored helicopter blade blown by a wind flow. The obtained nonlinear partial differential equation by the Galerkin`s method is reduced to a system of differential equations. The Newmark`s method is used for its numerical integration. Formulas are obtained for calculating boundaries of the regions of dynamic instability of moored and non-moored rotor blades of the helicopter. Based on the equations of parametric oscillations of blades, the critical frequencies and excitation coefficients corresponding to the main and two side resonances are determined
Flight simulation testing of a turbulence model based on a Synthetic Eddy Method
No full textThis paper presents initial analysis of an ongoing series of flight simulation trials of a new turbulence model based on a synthetic eddy method (SEM). The model is based on the generation of a random distribution of turbulence generating Eddies within a control model surrounding the aircraft. Eddies are displaced by the flow and regenerated at the inflow as they leave the simulation domain. The model allows adjustment of turbulence intensity by adjusting the value of Reynolds stress tensor and of frequency spectra through adjustment of eddy sizes, allowing for a more realistic representation of broadband turbulence. Compared to other random turbulence models, preserving the location of the Eddies in the control volume ensures automatically that turbulence across different aircraft locations is automatically correlated. Piloted flight simulation tests show that both, levels of turbulence intensity and frequency of the induced turbulence have a strong effect on workload and task performance. Increases in turbulence intensity result in a direct increase in pilot workload and reduced task performance. However changes in frequency of turbulence present a more complex picture dependent on flight condition and aircraft response
Electro-mechanical de-icing system for a non-rotating structure of small and medium sized helicopters
No full textThere is a high demand for de-icing systems with low energy consumption for small and medium sized helicopters. De-icing systems based on the electro-mechanical principle appear to be particularly energy efficient since they take advantage of structural resonance frequencies. However, this approach has its limitations in terms of structural conformity, operational aspects and environmental conditions. This paper investigates the design process of such an electro-mechanical de-icing system as well as its performance on a real helicopter structure during realistic icing conditions in a laboratory environment. A special focus is on the non-consideration of an ice layer during the design process. The optimized system is subsequently confirmed by experimental results that will help to bring the approach further towards industrial applications