scholarly journals Nonlinear flight physics of the Lie Bracket roll mechanism

2021 ◽  
Author(s):  
Haithem E. Taha ◽  
Ahmed Hassan ◽  
Moatasem Fouda
Keyword(s):  
Superior Performance ◽  
Nonlinear Interactions ◽  
Free Flight ◽  
Roll Control ◽  
Lie Bracket ◽  
Order Of Magnitude ◽  
Control Authority ◽  
Six Dof ◽  
Lie Brackets ◽  
Confined Environment

AbstractIn this paper, we review the concept of Lie brackets and how it can be exploited in generating motion in unactuated directions through nonlinear interactions between two or more control inputs. Applying this technique to the airplane flight dynamics near stall, a new rolling mechanism is discovered through nonlinear interactions between the elevator and the aileron control inputs. This mechanism, referred to as the Lie Bracket Roll Augmentation (LIBRA) mechanism, possesses a significantly higher roll control authority near stall compared to the conventional roll mechanism using ailerons only; it produces more than an order-of-magnitude stronger roll motion over the first second. The main contribution of this paper is to study the nonlinear flight physics that lead to this superior performance of the LIBRA mechanism. In fact, the LIBRA performance in free flight (six DOF) is double that in a confined environment of two-DOF roll-pitch dynamics. The natural feedback from the airplane motion (roll, yaw, and sideslip) into the LIBRA mechanism boosts its performance through interesting nonlinear interplay between roll and yaw, while exploiting some of the changes in the airplane characteristics near stall.

scholarly journals Diffusion model of interacting gravity waves on the surface of deep fluid

1999 ◽  
Vol 6 (1) ◽  
pp. 1-10 ◽  
Author(s):  
V. E. Zakharov ◽  
A. N. Pushkarev
Keyword(s):  
Gravity Waves ◽  
Good Description ◽  
Computer Time ◽  
Nonlinear Interactions ◽  
Real Situation ◽  
Diffusion Type ◽  
Numerical Studies ◽  
Order Of Magnitude ◽  
Deep Fluid ◽  
Interaction Term

Abstract. A simple phenomenological model for nonlinear interactions of gravity waves on the surface of deep water is developed. The Snl nonlinear interaction term in the kinetic equation for wave action is replaced by the nonlinear second-order diffusion-type operator. Analytical and numerical studies show that the new model gives a reasonably good description of a real situation, consuming three order of magnitude less computer time.

scholarly journals PETRA

2021 ◽  
Vol 18 (2) ◽  
pp. 1-26
Author(s):  
Ramin Izadpanah ◽  
Christina Peterson ◽  
Yan Solihin ◽  
Damian Dechev
Keyword(s):  
Data Structures ◽  
High Performance ◽  
Transactional Memory ◽  
Superior Performance ◽  
New Approach ◽  
Ordering Constraints ◽  
Level Information ◽  
Order Of Magnitude ◽  
Persistent Data ◽  
High Level

Emerging byte-addressable Non-Volatile Memories (NVMs) enable persistent memory where process state can be recovered after crashes. To enable applications to rely on persistent data, durable data structures with failure-atomic operations have been proposed. However, they lack the ability to allow users to execute a sequence of operations as transactions. Meanwhile, persistent transactional memory (PTM) has been proposed by adding durability to Software Transactional Memory (STM). However, PTM suffers from high performance overheads and low scalability due to false aborts, logging, and ordering constraints on persistence. In this article, we propose PETRA, a new approach for constructing persistent transactional linked data structures. PETRA natively supports transactions, but unlike PTM, relies on the high-level information from the data structure semantics. This gives PETRA unique advantages in the form of high performance and high scalability. Our experimental results using various benchmarks demonstrate the scalability of PETRA in all workloads and transaction sizes. PETRA outperforms the state-of-the-art PTMs by an order of magnitude in transactions of size greater than one, and demonstrates superior performance in transactions of size one.

scholarly journals The Lie Brackets on Time Scales

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
H. Kusak ◽  
A. Caliskan
Keyword(s):  
Time Scales ◽  
Lie Derivative ◽  
Two Dimensional ◽  
The Real ◽  
Numerical Example ◽  
Lie Bracket ◽  
Wide Range ◽  
Lie Brackets

The Lie derivative, which has a wide range of application in physics and geometry, is trying to be examined on time scales. Firstly, nabla Lie bracket is defined on two-dimensional time scales. Secondly, the nabla Lie multiplication and some properties are given on the time scales. Lastly, for analyzing the differences between the real Lie multiplication and the nabla Lie multiplication, a numerical example is given.

Design and Realization of a Compliant Adaptable Wing

2014 ◽  
Author(s):  
G. Molinari ◽  
M. Quack ◽  
A. F. Arrieta ◽  
M. Morari ◽  
P. Ermanni
Keyword(s):  
Closed Loop ◽  
Piezoelectric Actuators ◽  
Element Model ◽  
Fiber Composites ◽  
Roll Control ◽  
Shape Adaptation ◽  
Control Authority ◽  
Aeroelastic Simulations ◽  
Wing Morphing ◽  
Good Agreement

This paper presents the design, optimization, realization and testing of a novel wing morphing concept based on compliant structures actuated by Macro Fiber Composites. The geometry of the compliant morphing ribs is determined through multidisciplinary optimizations. The static and dynamic behavior of the wing, and the effect of activating the actuators, is assessed using 3-D aeroelastic simulations. The performance and manufacturability of a wing designed according to this approach are investigated. The achieved active deformations produce sufficient roll control authority to replace conventional ailerons. The numerical simulation for the conformal shape adaptation of the wing is compared to experimental results, showing good agreement. The aerodynamic and structural behavior of the introduced concept is investigated through a validated finite element model, revealing the potential of the presented morphing wing. A closed-loop controller driving high-voltage electronics counteracts the nonlinearity and hysteresis of the piezoelectric actuators, allowing for controlling the wings’ morphing level.

Solving the forward kinematics problem of six-DOF Stewart platform using multi-task Gaussian process

2012 ◽  
Vol 227 (1) ◽  
pp. 161-169 ◽  
Author(s):  
Jianjun He ◽  
Hong Gu ◽  
Zhelong Wang
Keyword(s):  
Gaussian Process ◽  
Stewart Platform ◽  
Flight Simulation ◽  
Superior Performance ◽  
Forward Kinematics ◽  
Real Time Processing ◽  
Process Learning ◽  
Training Samples ◽  
Six Dof ◽  
Six Degree Of Freedom

The forward kinematics problem of general six-degree-of-freedom Stewart platform is addressed in this article. Unlike the convention taking positional variables as independent ones and solving them individually, this article presents an alternative approach which takes the positional variables as multiple-related tasks and exploits the commonality between them using a multi-task Gaussian process learning method, as a result, a simple adaptive algorithm, which may satisfy the requirements for high accuracy and real-time processing, is established. Moreover, the proposed algorithm can achieve the desired accuracy using 1000 training samples at most, which is far less than those of other algorithms. Simulation results on a Stewart platform used in aircraft flight simulation system show that the proposed algorithm can achieve superior performance.

The covariant derivative and the curvature

2018 ◽  
Author(s):  
Nathalie Deruelle ◽  
Jean-Philippe Uzan
Keyword(s):  
Covariant Derivative ◽  
Tangent Space ◽  
Lie Derivative ◽  
Connected Manifold ◽  
Lie Bracket ◽  
Exterior Calculus ◽  
Lie Brackets ◽  
Set Of Points

This chapter first considers the tangent spaces of a non-connected manifold, in which the tangent t at the set of points p in the manifold is an element of the tangent space at p. Afterward, the chapter summarizes the elementary introduction to the exterior calculus of Chapter 5 of Book 2. Next, the chapter studies the Lie bracket and Lie derivative, before moving on to the covariant derivative and a connected manifold. The covariant derivative in particular is introduced to ensure the effectiveness of the Lie brackets and the Lie derivative. From here, this chapter considers the torsion of a covariant derivative and finally to the curvature of a covariant derivative.

scholarly journals Aerodynamics of MAV rotors in ground and corner effect

2019 ◽  
Vol 11 ◽  
pp. 175682931986159
Author(s):  
S Prothin ◽  
C Fernandez Escudero ◽  
N Doué ◽  
T Jardin
Keyword(s):  
Numerical Model ◽  
Flow Field ◽  
Research Work ◽  
Flow Analysis ◽  
Aerodynamic Performance ◽  
Free Flight ◽  
Corner Effect ◽  
Experimental Approaches ◽  
Confined Environment ◽  
Do So

The work presented in this paper is part of a project called ARChEaN (Aerodynamic of Rotors in Confined ENvironment) whose objective is to study the interactions of a micro drone rotor with its surroundings in the case of flight in enclosed environments such as those encountered, for example, in archeological exploration of caves. To do so the influence of the environment (walls, ground, ceiling, etc) on the rotor’s aerodynamic performance as well as on the flow field between the rotor and the surroundings is studied. This paper focuses on two different configurations, flight near the ground and flight near a corner (wall and ground), and the results are analyzed and compared to a general free flight case (i.e. far away from any obstacle). In order to carry out this analysis both numerical and experimental approaches are conducted. The objective is to validate the numerical model with the results obtained experimentally and to benefit from the advantages of both approaches in terms of flow analysis. This research work will provide knowledge on how to operate these systems as to minimize the possible negative environment disturbances, reduce power consumption and predict the micro drone’s behaviour during enclosed flights.

scholarly journals Ultrahigh Photocatalytic CO2 Reduction Efficiency by Single Metallic Atom Oxide on TiO2

2020 ◽  
Author(s):  
Yibo Feng ◽  
Cong Wang ◽  
Peixin Cui ◽  
Chong Li ◽  
Liyong Gan ◽  
...  
Keyword(s):  
Rational Design ◽  
Low Cost ◽  
Co2 Reduction ◽  
Superior Performance ◽  
Industrial Chemicals ◽  
Tungsten Atom ◽  
High Coverage ◽  
Reduction Efficiency ◽  
Order Of Magnitude ◽  
Novel Strategy

Abstract Photocatalytic carbon dioxide (CO2) reduction is a sustainable and energy-consumption-free route to directly convert the greenhouse gas into chemicals. Given the vast amount of greenhouse gases, numerous efforts have been devoted to developing inorganic photocatalysts due to their stable, low-cost and environmental-friendly properties. However, more efficient titanium dioxide (TiO2) without noble metal or sacrifice/organic agent is highly desirable for CO2 reduction practical application, and it is also difficult and urgently in demand for TiO2 producing selectively valuable compounds, i.e. industrial chemicals and fuels. Here, we develop a novel “adatom at step” strategy via anchoring single tungsten atom oxide (STAO) site on intrinsic steps of classic TiO2 nanoparticles. The composition of single-sites can be controlled by tuning the ratio of adatom W5+ to neighboring Ti3+, resulting in significant CO2 reduction efficiency and selectively yield of carbon monoxide (CO) or methane (CH4) as main products. The W5+-dominated catalysts can achieve an ultrahigh photocatalytic CH4 production of 59.3 μmol/g/h, while the Ti3+-dominated catalysts can achieve a CO production of 181.4 μmol/g/h, which both exceed those of pristine TiO2 by more than one order of magnitude. The mechanism relies on the accurate control of atomic sites with high coverage and the subsequent excellent electron-hole separation along with favorable adsorption-desorption of intermediates on sites. This approach not only provides a novel strategy for inorganic catalytic single-sites with superior performance, but also identifies the rational design mechanisms of the efficient site with controllable production.

Reduction of Residual Transient Photocurrents in A Si:H Elevated Photodiode Array Based Cmos Image Sensors

2005 ◽  
Vol 869 ◽  
Author(s):  
Jeremy A. Theil
Keyword(s):  
Crystalline Silicon ◽  
Image Sensors ◽  
Superior Performance ◽  
Sensor Performance ◽  
Cmos Image Sensors ◽  
Order Of Magnitude ◽  
Variable Bias ◽  
Photodiode Arrays ◽  
The One ◽  
Staebler Wronski Effect

AbstractWhile a-Si:H based elevated photodiode arrays hold the promise of superior performance and lower cost CMOS-based image sensors relative to those based upon crystalline silicon photodiodes, the one area where a-Si:H based sensor performance has not been as good is in image lag. This problem is only exacerbated by Staebler Wronski Effect induced junction degradation. Image lag is caused by residual charge from photocurrents trapped within the junction once the light source is removed and can be measured for several seconds, even under continuous applied reverse bias. It is seen both in constant and variable bias pixel architectures. However, by carefully controlling a-Si:H junction bias conditions, it is possible to significantly reduce these transient photocurrents. This article will describe how the photocurrent decay time exponent can be reduce by almost an order of magnitude. Finally the physical causes behind image lag in a-Si:H based photodiode arrays will be discussed.

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