Modelling of a Hybrid UAV Using Test Flight Data

Aircraft Engineering and Aerospace Technology, 2021

Purpose-This paper aims to overcome the main obstacle to compare the merits of the different control strategies for fixed-wing unmanned aerial vehicles (UAVs) to assess autopilot performances. Up to now, the published studies of control strategies have been carried out over disperse models, thus being complicated, if not impossible, to compare the merits of each proposal. The authors present a worked benchmark for autopilots studies, consisting of generalized models obtained by merging UAVs' parameters gathered from selected literature (journals) with other parameters directly obtained by the authors to include some relevant UAVs whose models are not provided in the literature. To obtain them it has been used a dedicated software (from U.S. Air Force). Design/methodology/approach-The proposed models have been constructed by averaging both the main aircraft defining parameters (model derivatives) and pole-zero locations of longitudinal transfer functions. The suitability of the used methodologies has been checked from their capability to fit the short period and the phugoid modes. Previous analytical model arrangement has been required to match a uniform set of parameters, as the inner state variables are neither the same along the different published models nor between the additional models the authors have here contributed. Besides, moving models between the space state representation and transfer function is not just a simple averaging process, as neither the parameters nor the model orders are the same in the different published works. So, the junction of the models to a common set of parameters requires some residual's computation and transient responses assessment (even Fourier analysis has been included to preserve the dominance of the phugoid) to keep the main properties of the models. The least mean squares technique has been used to have better fittings between SISO model parameters with state-space ones. Findings-Both the SISO (Laplace) and state-space models for the longitudinal transfer function of an "averaged" fixed-wing UAV are proposed. Research limitations/implications-More complicated situations, such as strong wind conditions, need another kind of models, usually based on finite element method simulation. These particular models apply fluid dynamics to study aerostructural aircraft aspects, such as flutter and other aerolastic aspects, the behavior under icing conditions or other distributed parameter problems. Even some models aim to control other aspects than the autopilot, such as the trajectory prediction. However, these models are not the most suitable for the basic UAV autopilot design (early design), so they are outside the objective of this paper. Obviously, the here-considered UAVs are not all the existing ones, but the number is large enough to consider the result as a reliable and realistic representation. The presented study may be seen as a stepping stone, allowing to include other UAVs in future works. Practical implications-The proposed models can be used as benchmarks, or as a previous step to produce improved benchmarks, in order to have a common and realistic scenario the compare the benefits of the different control actions in UAV autopilots continuously presented in the published research. Originality/value-A work with the scope of the presented one, merging model parameters from literature with other (often referred in papers and websites) whose parameters have been obtained by the authors has been never published.

International Journal of Engineering Research and, 2015

Hybrid aircrafts are unique type of aircrafts that combine the hover capability of helicopters with the speed and range of airplanes. In this work, we propose a novel hybrid aircraft based on the fixed-wing airplane and quad rotor structures. A complete mathematical model of the aircraft, in helicopter, transition and airplane flight modes is presented. Finally, simulation results are presented in order to illustrate performances of the proposed controller. The proposed UAV structure configuration is similar to V-22 osprey however it is designed based on the propeller thrust instead of jetengines In any hybrid aircraft, the transition between hover flight and cruise flight is the most difficult regime to achieve and convertible rotor aircraft are no exception to this The design has been developed as UAV which is propelled by motors which has all the abilities of flight controls equipped in a single body. Which has a specification of weight up to 4kg's Future work will consist of creating a more detailed model for lift and drag..

2018 International Conference on Unmanned Aircraft Systems (ICUAS)

Transitioning vehicles experience three different flight phases during typical missions. The hovering and forward flight phases have been researched widely, however the transition phase in between is more challenging and has been the subject of less research. One of the control approaches to handle the transition phase relies on model-based methods which require sophisticated wind-tunnel characterization. Accurate modeling of force and moments of a partially stalled wing and control surfaces is highly challenging and time consuming. In addition, these models usually require several flight measurements (such as angle of attack and low airspeed) that are difficult to obtain. As an alternative, some control approaches manage the transition phase without the need for sophisticated models. One example of such an approach is the Model Free Control (MFC). This paper compares the results obtained from both MFC and Linear Quadratic Regulator (LQR) applied to fixed-wing UAV with transitioning flight capability during hovering, transition and forward flight modes. Both of the controllers are designed for a transitioning vehicle called MAVion. The simulation results demonstrated that MFC increases the stability of the aircraft, especially in disturbed flight conditions.

—A Hybrid Unmanned Aerial Vehicle (UAV) has both advantages of multirotor and fixed-wing UAV. This unique design leads to a more complicated airframe and control design compared to those of a conventional drone. Integrating two platform of UAV (multirotor and fixed-wing) also requires carefully consideration to safely operate this hybrid UAV. This paper discussed the flight scenario that includes flight modes and parameters to be determined before flight. This leads to the development of the flight procedure as an important prerequisite for a successful flight.

Aircraft engineering, 2010

Purpose-The purpose of this paper is to describe the longitudinal dynamics of a hover-capable rigid-winged unmanned aerial vehicles (UAV) under various equilibrium flight conditions. The effects of the variable-incidence wing in comparison with the fixed in-incidence wing on the dynamics of UAV are also discussed. Design/methodology/approach-The aerodynamic modeling of the vehicle covers both pre-stall and post-stall regimes using a three-dimensional vortex lattice method incorporating viscous corrections. The trim states across a velocity spectrum are evaluated using a nonlinear constrained optimization scheme based on sequential quadratic programming. Then linearized dynamic analysis around trim states is carried out in order to compare the characteristics of the conventional platform with the modified platform incorporating variable-incidence wing. Findings-It is found that with the variable-incidence wing, the longitudinal equilibrium flights can be achieved with reduced thrust-to-weight ratio demands and lower elevator deflection. However, the use of the variable-incidence wing changes the dynamic characteristics of the vehicle considerably as indicated through the linear dynamic analysis. Research limitations/implications-The results presented in this paper are based on linear dynamic analysis about static trim point data. Further analysis taking into account nonlinearity, the unsteady aerodynamic effects and associated cross-coupling because of asymmetric forces may be needed to reveal the true dynamics of the vehicle under unsteady maneuvers. Practical implications-The variable-incidence wing is a useful design feature to reduce the thrust-to-weight ratio requirements and to increase elevator control authority, however its effect on the dynamics warrants further investigation. Originality/value-This is the first paper highlighting the effects of variable-incidence wing on an agile hover-capable UAV.