A Flight Dynamics Model for a Small-Scale Flybarless Helicopter

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Skander Taamallah
Keyword(s):  
Nonlinear Model ◽  
Flight Dynamics ◽  
Small Scale ◽  
Helicopter Flight ◽  
Bandwidth Control ◽  
High Bandwidth ◽  
Flight Dynamics Model ◽  
Vortex Ring State ◽  
Good Agreement ◽  
Made In

We present a helicopter flight dynamics nonlinear model for a flybarless, articulated, pitch–lag–flap (P–L–F) main rotor (MR) with rigid blades, particularly suited for small-scale unmanned aerial vehicles (UAVs). The model incorporates the MR, tail rotor (TR), fuselage, and tails. This model is further applicable for high bandwidth control specifications and is valid for a range of flight conditions, including the vortex-ring-state (VRS) and autorotation. Additionally, the paper reviews all assumptions made in deriving the model, i.e., structural, aerodynamics, and dynamical simplifications. Simulation results show that this nonlinear model is in good agreement with an equivalent flightlab model, for both static (trim) and dynamic conditions.

Comprehensive Nonlinear Modeling of a Miniature Unmanned Helicopter

2012 ◽  
Vol 57 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Guowei Cai ◽  
Ben M. Chen ◽  
Tong H. Lee ◽  
Kai-Yew Lum
Keyword(s):  
Nonlinear Model ◽  
Nonlinear Modeling ◽  
Flight Dynamics ◽  
Rigid Body Dynamics ◽  
Parameter Determination ◽  
Small Scale ◽  
Dynamics Model ◽  
Unknown Parameters ◽  
Essential Components ◽  
Flight Dynamics Model

A nonlinear flight dynamics model that can be adopted by small-scale unmanned aerial vehicle (UAV) helicopters is presented. To minimize structural complexity, the proposed nonlinear model contains only four essential components, i.e., kinematics, rigid-body dynamics, main rotor flapping dynamics, and yaw rate feedback controller dynamics. A five-step parameter determination procedure is proposed to estimate the unknown parameters of the flight dynamics model. Based on the time-domain evaluations conducted, the nonlinear model is proven to be accurate in capturing the flight dynamics of our UAV helicopter platform over a wide envelope.

Trajectory Simulations for Laser-Launched Microsatellites Using a 7-DOF Flight Dynamics Model

2009 ◽  
Author(s):  
David A. Kenoyer ◽  
Kurt S. Anderson ◽  
Leik N. Myrabo
Keyword(s):  
Laser Beam ◽  
Specific Impulse ◽  
Flight Dynamics ◽  
Basic Research ◽  
Scale Model ◽  
Beam Power ◽  
Small Scale ◽  
Dynamics Model ◽  
Predictive Tool ◽  
Flight Dynamics Model

Laser launch trajectories are being developed for boosting nano- and micro-satellite sized payloads (i.e., 1 to 100 kg) using a 7-Degree Of Freedom (DOF) flight dynamics model that has been extensively calibrated against 16 actual trajectories of small scale model lightcraft flown at White Sands Missile Range, NM on a 10 kW pulsed CO2 laser called PLVTS. The full system 7-DOF model is comprised of individual aerodynamics, engine, laser beam propagation, variable vehicle inertia, reaction controls system, and dynamics models, integrated to represent all major phenomena in a consistent framework. The suborbital trajectory results presented herein are for a 240 cm diameter lightcraft (100 kg payload; 100 MW beam power) flown under three different laser-boost scenarios: 1) liftoff and vertical climb-out on a vertically oriented laser beam; 2) liftoff and climb-out along a constant laser beam pointing angle (fixed azimuth and zenith) defined relative to the launch pad; 3) liftoff and climb-out on a beam with a time-varying pointing schedule (azimuth and zenith) to “slingshot” the lightcraft laterally, making maximum use of the engine’s autonomous beam-riding feature. For simplicity, simulations assume a solid ablative rocket propellant (e.g., Teflon®-like performance) with a vacuum specific impulse of 644 seconds, momentum coupling coefficient of 190 N/MW, and overall efficiency of 60%. This flight dynamics model and associated 7-DOF code provide a physics-based predictive tool for basic research investigations into laser launched lightcraft for suborbital and orbital missions. An investigative protocol was developed to identify and quantify phenomena that dominate each phase of the launch trajectory. These protocols are specified herein, along with physics-based explanations for such phenomena, both predicted and observed.

scholarly journals Investigation on effects of time-frequency characteristics of ship airwake on helicopter flight characteristics

2021 ◽  
Vol 39 (5) ◽  
pp. 1087-1096
Author(s):  
Jinghui DENG
Keyword(s):  
Flight Dynamics ◽  
Critical Factors ◽  
Dynamics Model ◽  
Time Frequency ◽  
Helicopter Flight ◽  
Unsteady Loading ◽  
Flight Dynamics Model ◽  
The One ◽  
Yaw Moment ◽  
Spatial And Temporal Characteristics

A conventional helicopter flight dynamics model, which can be coupled with ship airwake date, is developed in this study. In the method, the ship airwake data is obtained by the high-accuracy DES model, and a strategy which can transmit CFD data to the flight dynamics model is established based on the "one-way" coupling idea. Then, the SFS2 ship model and UH-60A helicopter are chosen as a combination to investigate the influences of the spatial and temporal characteristics of ship airwake from the aspects of control margins and unsteady level. The time-averaged simulation results show that for the counterclockwise-rotor helicopter, although pilot could have more collective pitch margin under crosswind condition compared to the headwind condition, he might possess much less pedal margin due to the sidewash in the airflow. The unsteady results indicate that the unsteady loading level of the helicopter would increase significantly under the crosswind condition compared to the headwind condition due to the increase of turbulent density in the airwake. Furthermore, for the conventional helicopter, the disturbances on the forces and moments which along the rotor hub (i.e., thrust and yaw moment) are the critical factors that increasing the pilot workload during the landing procedure.

scholarly journals Parameterized Model of Flight Dynamics of the Transport Helicopter

2020 ◽  
Vol 50 (3) ◽  
pp. 237-256
Author(s):  
Piotr Golański ◽  
Marek Szczekala ◽  
Jerzy Manerowski ◽  
Michał Roguszewski
Keyword(s):  
Mixed Reality ◽  
Flight Dynamics ◽  
Flight Test ◽  
Real Object ◽  
Test Results ◽  
Dynamics Model ◽  
Test Characteristics ◽  
Helicopter Flight ◽  
Parameterized Model ◽  
Flight Dynamics Model

AbstractThe article addresses investigating the possibilities of making a parameterized flight dynamics model in a mixed reality environment. The purpose was to obtain a model for a Mi-17 helicopter. The Mi-17 VI helicopter flight test characteristics were used to evaluate the above model. As a comparative criterion, compatibility between the model’s selected characteristics and the real object was adopted. Simulation tests were conducted on a cabin simulator set made via MR (mixed reality) technology. Test results confirmed the possibility of reconstructing the selected helicopter type’s flight dynamics using the parameterized model.

scholarly journals Experimental and Numerical Investigation about Small Clearance Journal Bearings under Static Load Conditions

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Carlo Alberto Niccolini Marmont Du Haut Champ ◽  
Fabrizio Stefani ◽  
Paolo Silvestri
Keyword(s):  
Three Dimensional ◽  
Journal Bearings ◽  
Radial Clearance ◽  
Small Scale ◽  
Test Rig ◽  
Small Clearance ◽  
Dimensional Simulation ◽  
Dynamic Loading Conditions ◽  
Static And Dynamic Loading ◽  
Good Agreement

The aim of the present research is to characterize both experimentally and numerically journal bearings with low radial clearances for rotors in small-scale applications (e.g., microgas turbines); their diameter is in the order of ten millimetres, leading to very small dimensional clearances when the typical relative ones (order of 1/1000) are employed; investigating this particular class of journal bearings under static and dynamic loading conditions represents something unexplored. To this goal, a suitable test rig was designed and the performance of its bearings was investigated under steady load. For the sake of comparison, numerical simulations of the lubrication were also performed by means of a simplified model. The original test rig adopted is a commercial rotor kit (RK), but substantial modifications were carried out in order to allow significant measurements. Indeed, the relative radial clearance of RK4 RK bearings is about 2/100, while it is around 1/1000 in industrial bearings. Therefore, the same original RK bearings are employed in this new test rig, but a new shaft was designed to reduce their original clearance. The new custom shaft allows to study bearing behaviour for different clearances, since it is equipped with interchangeable journals. Experimental data obtained by this test rig are then compared with further results of more sophisticated simulations. They were carried out by means of an in-house developed finite element (FEM) code, suitable for thermoelasto-hydrodynamic (TEHD) analysis of journal bearings both in static and dynamic conditions. In this paper, bearing static performances are studied to assess the reliability of the experimental journal location predictions by comparing them with the ones coming from already validated numerical codes. Such comparisons are presented both for large and small clearance bearings of original and modified RKs, respectively. Good agreement is found only for the modified RK equipped with small clearance bearings (relative radial clearance 8/1000), as expected. In comparison with two-dimensional lubrication analysis, three-dimensional simulation improves prediction of journal location and correlation with experimental results.

scholarly journals An approach to the modeling of a virtual thermal manikin

2014 ◽  
Vol 18 (4) ◽  
pp. 1413-1423 ◽  
Author(s):  
Dragan Ruzic ◽  
Sinisa Bikic
Keyword(s):  
Turbulence Models ◽  
Thermal Conditions ◽  
Heat Fluxes ◽  
Thermal Manikin ◽  
Flow Conditions ◽  
Body Segments ◽  
Nominal Size ◽  
Natural Flow ◽  
Good Agreement ◽  
Made In

The aim of the research described in this paper, is to make a virtual thermal manikin that would be simple, but also robust and reliable. The virtual thermal manikin was made in order to investigate thermal conditions inside vehicle cabins. The main parameters of the presented numerical model that were investigated in this paper are mesh characteristics and turbulence models. Heat fluxes on the manikin's body segments obtained from the simulations were compared with published results, from three different experiments done on physical thermal manikins. The presented virtual thermal manikin, meshed with surface elements of 0.035 m in nominal size (around 13,600 surface elements) and in conjunction with the two-layer RANS Realizable k-? turbulence model, had generally good agreement with experimental data in both forced and natural flow conditions.

Heat-flow experiments in liquid 4He with a variable cylindrical geometry

1987 ◽  
Vol 174 ◽  
pp. 209-231 ◽  
Author(s):  
H. Gao ◽  
G. Metcalfe ◽  
T. Jung ◽  
R. P. Behringer
Keyword(s):  
Cylindrical Geometry ◽  
Small Scale ◽  
Onset Of Convection ◽  
Aspect Ratios ◽  
A Value ◽  
Prandtl Numbers ◽  
Convection Rolls ◽  
Flow Experiments ◽  
Increasing Function ◽  
Good Agreement

This paper first describes an apparatus for measuring the Nusselt number N versus the Rayleigh number R of convecting normal liquid 4He layers. The most important feature of the apparatus is its ability to provide layers of different heights d, and hence different aspect ratios [Gcy ]. The horizontal cross-section of each layer is circular, and [Gcy ] is defined by [Gcy ] = D/2d where D is the diameter of the layer. We report results for 2.4 [les ] [Gcy ] [les ] 16 and for Prandtl numbers Pr spanning 0.5 [lsim ] Pr [lsim ] 0.9 These results are presented in terms of the slope N1 = RcdN/dR evaluated just above the onset of convection at Rc. We find that N1 is only a slowly increasing function of [Gcy ] in the range 6 [lsim ] [Gcy ] [lsim ] 16, and that it has a value there which is quite close to 0.72. This value of N1 is in good agreement with variational calcuations by Ahlers et al. (1981) pertinent to parallel convection rolls in cylindrical geometry. Particularly for [Gcy ] [lsim ] 6, we find additional small-scale structure in N1 associated with changes in the number of convection rolls with changing [Gcy ]. An additional test of the linearzied hydrodynamics is given by measurements of Rc. We find good agreement between theory and our data for Rc.

scholarly journals Post-liquefaction reconsolidation of sand

2016 ◽  
Vol 472 (2186) ◽  
pp. 20150745 ◽  
Author(s):  
O. Adamidis ◽  
G. S. P. Madabhushi
Keyword(s):  
Void Ratio ◽  
One Dimensional ◽  
Geotechnical Centrifuge ◽  
Significant Damage ◽  
Pore Water Pressures ◽  
The One ◽  
Crucial Parameter ◽  
Excess Pore ◽  
Good Agreement ◽  
Made In

Loosely packed sand that is saturated with water can liquefy during an earthquake, potentially causing significant damage. Once the shaking is over, the excess pore water pressures that developed during the earthquake gradually dissipate, while the surface of the soil settles, in a process called post-liquefaction reconsolidation. When examining reconsolidation, the soil is typically divided in liquefied and solidified parts, which are modelled separately. The aim of this paper is to show that this fragmentation is not necessary. By assuming that the hydraulic conductivity and the one-dimensional stiffness of liquefied sand have real, positive values, the equation of consolidation can be numerically solved throughout a reconsolidating layer. Predictions made in this manner show good agreement with geotechnical centrifuge experiments. It is shown that the variation of one-dimensional stiffness with effective stress and void ratio is the most crucial parameter in accurately capturing reconsolidation.

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