Performance and Design Investigation of Heavy Lift Tiltrotor with Aerodynamic Interference Effects
01 May 2007-
TL;DR: In this article, the aerodynamic interference effects on tiltrotor performance in cruise were investigated using comprehensive calculations, to better understand the physics and to quantify the effects on the aircraft design.
Abstract: Abstract : The aerodynamic interference effects on tiltrotor performance in cruise are investigated using comprehensive calculations, to better understand the physics and to quantify the effects on the aircraft design. Performance calculations were conducted for 146,600-lb conventional and quad tiltrotors, which are to cruise at 300 knots at 4000 ft/95 deg F condition. A parametric study was conducted to understand the effects of design parameters on the performance of the aircraft. Aerodynamic interference improves the aircraft lift-to-drag ratio of the baseline conventional tiltrotor. However, interference degrades the aircraft performance of the baseline quad tiltrotor, due mostly to the unfavorable effects from the front wing to the rear wing. A reduction of rotor tip speed increased the aircraft lift-to-drag ratio the most among the design parameters investigated.
22 Sep 2017
TL;DR: In this paper, a modifizierte, instationare Wirbelgittermethode vorgestellt, die mittels Windkanalversuchen validiert wird.
Abstract: In diesem Artikel wird eine modifizierte, instationare Wirbelgittermethode vorgestellt, die mittels Windkanalversuchen validiert wird. Diese Methode wird auf einen hybriden Flugzeugtyp, der aus einer Kombination eines Flachenflugzeugs mit einem Multirotorsystem besteht, angewendet. Dieser Flugzeugtyp wird in drei verschiedenen Flugphasen betrieben: Dem Schwebeflug, dem Schnellflug und der Transition, die den Ubergang zwischen Schwebeflug und Schnellflug darstellt. Die Modellierung dieser Flugzeugkonfiguration ist vor allem im Schwebeflug und der Transition interessant, da in diesen Flugphasen viele verschiedene aerodynamische Effekte, wie Propellerinterferenzen, Stromungsablosung, Wirbelinteraktionen und Schlagen der Propellerblatter auftreten. Um die dominanten aerodynamischen Effekte in erster Naherung zu bestimmen, wurde eine modifizierte Wirbelgittermethode entwickelt, die dies mit geringem Rechenaufwand ermoglicht. Die Validierung der Methode erfolgt mit Windkanaltests eines skalierten Modells der betrachteten Flugzeugkonfiguration. Der vorgestellte Modellierungsansatz zeigt eine gute Ubereinstimmung mit den Windkanalergebnissen. Es wird erwartet, dass die Methode zur Berechnung der Aerodynamik von ahnlichen Flugzeugkonfigurationen anwendbar ist.
08 Jun 2023
TL;DR: In this paper , a data-driven modeling of electric vertical take off and landing vehicles (eVTOLs) based on deep learning networks is developed, which is similar to the NASA X-57 Maxwell aircraft with a tilt rotor at the wing tip.
Abstract: Electric Vertical Take Off and Landing vehicles (eVTOL) show significant promise for the Urban Air Mobility in the near future. Vectored thrust and Lift-Cruise configurations with distributed electric propulsion are the most popular configurations being investigated in addition to many unique configurations. However, the physics based flight dynamic modeling of these eVTOL configurations are complex as it involves the aero-propulsive interactions, transition flight dynamics and unexpected scenarios in the urban environment. Therefore, in this study, Data driven modeling of eVTOL Flight Dynamic model, based on Deep learning networks, is developed. An eVTOL configuration similar to the NASA’s X-57 Maxwell aircraft with a tilt rotor at the wing tip is considered. The structural and flight parametric values are considered from the experimentally validated prototype available in the previous study. Initially, a nonlinear flight dynamic model of transition flight from hover to cruise is modeled with Newton-Euler equations. The transition flight is achieved by tilting the rotors at the wing tip. Tilt rotor induced aerodynamic effects are included with models varying from low fidelity to high fidelity. The transition flight dynamic response data is created with the numerical simulations. In the next stage, two Data driven approaches are investigated to approximate the transition flight dynamics. The data driven models capturing the local and global flight dynamic behaviour are developed. Deep learning nets based on Recurrent Neural Network (RNN) and Multilayer Neural Network are used accordingly. A preliminary numerical results are obtained with the simple aerodynamic models coupled with tilt rotor dynamics. The DD model for global behavior is developed with various tilt angle rate and the corresponding flight response. The DD models show moderate accuracy for some flight response and perform badly for some flight responses. In the full paper, DD models will be developed based Long Short Term Memory based on RRN neural nets to improve the accuracy. The DD model for local behavior, at each flight state, will also be developed. Further the aero-propulsive interaction models will be used to simulate the data closer to the real flight date. This study will show the feasibly of full automation of the modeling and control of eVTOL.
TL;DR: In this article , a computational fluid dynamics simulation method is developed to study the influence of the rotor overlapping azimuth on the aerodynamic performance of compound coaxial helicopter in hover and forward.
Abstract: In this paper, a computational fluid dynamics simulation method is developed to study the influence of the rotor overlapping azimuth on the aerodynamic performance of compound coaxial helicopter. The simulation method is verified by comparing the numerical simulation results with the wind tunnel experiment data of the NASA coaxial rotor. Two overlapping azimuths of the upper and lower blades are considered, and the aerodynamic performance of the isolated rotor and the compound coaxial helicopter in hover and forward are analyzed respectively. State 1 means the upper and lower blades overlap at azimuth 0/180° or 90/270°, state 2 means the upper and lower blades overlap at azimuth 45/225° or 135/315°. It is found that the performance of isolated rotors is not affected by rotor overlapping azimuth in hover, but the total thrust fluctuation amplitude of isolated rotors in state 2 is 76.3% smaller than that in state 1 in forward. In the hovering flight of compound coaxial helicopter, compared with state 1, the fluctuation amplitude of the lift of the wing in state 2 is 42.7% smaller; the lift fluctuation amplitude of the flat tail in state 2 is 52.4% smaller. In the forward flight of compound coaxial helicopter, compared with state 1, the total thrust fluctuation amplitude in state 2 is 83.5% smaller; the fluctuation amplitude of the lift of the wing in state 2 is 61.2% smaller. It can be concluded that the compound coaxial helicopter working in state 2 has better aerodynamic performance than the compound coaxial helicopter working in state 1; changing the rotor overlapping azimuth of the upper and lower rotors has a high engineering application value, which can increase aerodynamic stability and reduce lift fluctuations.
25 Nov 2022
TL;DR: In this paper , a transition mode model of tilt trirotor unmanned aerial vehicle (UAV), combined with a fuzzy modeling method based on TSK fuzzy model, is proposed to solve the flight state variables, such as attitude, altitude and speed, more quickly and accurately.
Abstract: Focusing on the high cost and complex operation in establishing the transition mode model of tilt trirotor unmanned aerial vehicle (UAV), combined with a fuzzy modeling method based on TSK fuzzy model. Firstly, the flight data of UAV are collected through simulation. Secondly, the membership function of TSK fuzzy model is designed according to the expert experience, and constant variable mass and moment of inertia is added to the data set of the neural network for Supervised learning and rapid convergence. Finally, the predictive control law is designed. Based on simulation platform, the off-line model is simulated under a fixed tilt curve which prove the effectiveness of the method. The experimental results show that this method can solve the flight state variables, such as attitude, altitude and speed, more quickly and accurately, and this method greatly reduces the cost of model identification.
TL;DR: TRUAV structural features, dynamics modeling, and flight control methods are discussed, and major challenges and corresponding developmental tendencies associated with TRUAV flight control are summarized.
TL;DR: A complete six-degree-of-freedom nonlinear mathematical model of a tilt rotor unmanned aerial vehicle (UAV) for the design of a hover to forward flight and forward flight to hover transition control system and shows the successful transition of TURAC in experiment.
Abstract: This paper describes a complete six-degree-of-freedom nonlinear mathematical model of a tilt rotor unmanned aerial vehicle (UAV). The model is specifically tailored for the design of a hover to forward flight and forward flight to hover transition control system. In that respect, the model includes the aerodynamic effect of propeller-induced airstream which is a function of cruise speed, tilt angle and angle of attack. The cross-section area and output velocity of the propeller-induced airstream are calculated with momentum theory. The projected area on the UAV body that is affected by the propeller-induced airstream is specified and 2D aerodynamic analyses are performed for the airfoil profile of this region. Lookup-tables are generated and implemented in the nonlinear mathematical model. In addition, aerodynamic coefficients of the airframe are calculated by using CFD method and these data are embedded into the nonlinear model as a lookup-table form. In the transition flight regime, both aerodynamic and thrust forces act on the UAV body and the superimposed dynamics become very complex. Hence, it is important to define a method for hover-to-cruise and cruise-to-hover transitions. To this end, both transition scenarios are designed and a state-schedule is developed for flight velocity, angle of attack, and thrust levels of each of the thrust-propellers. This transition state schedule is used as a feedforward state for the flight control system. We present the simulation results of the transition control system and show the successful transition of TURAC in experiment.
01 Jul 2008
TL;DR: In this paper, a large civil tiltrotor (LCTR2) is designed to carry 90 passengers for 1000 nm or greater, with performance of 300 knots at 28,000ft altitude.
Abstract: : Performance optimization and analysis is presented for a Large Civil Tiltrotor (LCTR2). Intended to replace regional airliners over medium ranges, LCTR2 is designed to carry 90 passengers for 1000 nm or greater, with performance of 300 knots at 28,000-ft altitude. Design features include low hover and cruise tip speeds of 650 and 350 ft/sec, respectively. The paper is primarily concerned with rotor aerodynamic optimization for performance, including rotor/wing interference calculations. Twist, taper, and solidity optimizations are presented, along with an analysis of flight performance in turns. Hover/cruise performance tradeoffs for different cruise tip speeds are also presented. A free-wake model was used for all rotor analyses, computed by the CAMRAD II comprehensive analysis code. Aircraft design was done with the RC sizing code, developed by the U. S. Army Aeroflightdynamics Directorate.
TL;DR: This study shows both the common parts and the fundamental differences in the modeling, guidance, control, and control allocation for each hybrid-VTOL-UAV type.
28 May 2013
TL;DR: In this article, the authors proposed an alternative propulsion system formed by tilting rotors, which eliminates the need of tilting the airframe, and it suggests superior performance with respect to regular quadrotor design.
Abstract: The use of unmanned aerial vehicles (UAVs) for military, scientific, and civilian sectors are increasing drastically in recent years. The quadrotor platform has been used for many applications and research studies, as well. One of the limiting factors that prevents further implementation of the quadrotor system into applications, is the way quadrotor moves. It needs to tilt along the desired direction of motion. By doing this it can have necessary acceleration towards that direction. But tilting has the undesired effect of moving the onboard cameras' direction of view. This becomes an issue for surveillance and other vision based tasks. This study presents the design and control of a novel quadrotor system. Unlike previous study that uses regular quadrotor, this study proposes an alternative propulsion system formed by tilting rotors. This design eliminates the need of tilting the airframe, and it suggests superior performance with respect to regular quadrotor design. The mathematical model of the tiltable-rotor type quadrotor and designed control algorithms are explained. Various simulations are developed on MATLAB, in which the proposed quadrotor aerial vehicle has been successfully controlled. Comparison of the proposed system to regular quadrotor suggests better performance.
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