Use Of Control Surfaces Research Articles

Spin-leap performance by cetaceans is influenced by moment of inertia.

Cetaceans are capable of extraordinary locomotor behaviors in both water and air. Whales and dolphins can execute aerial leaps by swimming rapidly to the water surface to achieve an escape velocity. Previous research on spinner dolphins demonstrated the capability of leaping and completing multiple spins around their longitudinal axis with high angular velocities. This prior research suggested the slender body morphology of spinner dolphins together with the shapes and positions of their appendages allowed for rapid spins in the air. To test whether greater moments of inertia reduced spinning performance, videos and biologging data of cetaceans above and below the water surface were obtained. The principal factors affecting the number of aerial spins a cetacean can execute were moment of inertia and use of control surfaces for subsurface corkscrewing. For spinner dolphin, Pacific striped dolphin, bottlenose dolphin, minke whale and humpback whale, each with swim speeds of 6-7ms-1, our model predicted that the number of aerial spins executable was 7, 2, 2, 0.76 and 1, respectively, which was consistent with observations. These data implied that the rate of subsurface corkscrewing was limited to 14.0, 6.8, 6.2, 2.2 and 0.75 rad s-1 for spinner dolphins, striped dolphins, bottlenose dolphins, minke whales and humpback whales, respectively. In our study, the moment of inertia of the cetaceans spanned a 21,000-fold range. The greater moments of inertia for the last four species produced large torques on control surfaces that limited subsurface corkscrewing motion and aerial maneuvers compared with spinner dolphins.

Hovering Locomotion for UAVs With Thrust-Vectoring Control Surfaces

This letter presents a working prototype of a quad-rotor with control surfaces positioned in the propulsive slipstreams. The control surfaces provide a unique potential to redirect the air flow from the propulsion systems and produce lateral forces at a level attitude. This approach to locomotion has many useful applications in different areas of aerial sensing. Furthermore, the mechanical approach of using control surfaces for this purpose is unique, to the best of the authors’ knowledge; until this point, most aerial robot designs that have this locomotion capability make exclusive use of motors and propellers to exert lateral forces. The use of control surfaces in a propeller slipstream poses a potentially useful actuation mode for aerial vehicle designs that have control surfaces. The letter investigates lateral forces from redirected slipstreams as part of a larger development of the Multi-Section (MIST) Unmanned Aerial Vehicle at the University of Minnesota. The paper connects theoretical models with experiments on a testbed and a working prototype that demonstrate feasibility and characterize the force-production capability of slipstream-washed control surfaces.

Manoeuvring prediction of a container ship in shallow water using numerical planar motion mechanism

ABSTRACT Manoeuvring behaviour of a vessel changes drastically when it enters from deep water region to a shallow water region. Flow characteristics, around the hull changes and the vessel, respond poorly to the use of control surfaces. Aim of this paper is to study the manoeuvring behavioural changes in a container ship for different water depth conditions. Computational fluid dynamic (CFD) methods are used for simulating static and dynamic captive model tests. Variation in hydrodynamic reaction forces and moments caused by the reduction in water depth and the subsequent effect in hydrodynamic derivatives appearing in the equation of motion are explained in detail. Standard turning circle and zigzag manoeuvring tests are simulated using the CFD generated hydrodynamic derivatives to assess the manoeuvring characteristics of the vessel.

In-Flight Strain Monitoring of Aircraft Tail Boom Structure Using a Fiber Bragg Grating Sensor Based Health and Usage Monitoring System

With the increased use of composite materials in aircraft structures, continuous and thorough monitoring of structural conditions is highly required for the assurance of safety and reliability. In this study, as part of the fiber Bragg grating (FBG) sensor-based aircraft health and usage monitoring system (HUMS) development research, in-flight strain monitoring of an aircraft tail boom structure using the FBG sensor-based aircraft HUMS was investigated. The FBG sensor-based aircraft HUMS was implemented to the tail boom structure of an ultralight propeller composite aircraft. Flight tests of the testbed aircraft were performed, and in-flight strain variations of the tail boom structure were measured using the implemented system. For in-flight strain variation data-based verification through comparative analysis with flight parameters, the in-flight strain variations of the tail boom structure were analyzed with the flight parameters for various flight conditions. As a result, the HUMS operated as expected during the actual flights, and the acquired in-flight strain variations corresponded adequately in relation to the loading conditions during flight, such as bending loads due to the use of control surfaces and ground impacts during landing procedures.

Flight control system design with H∞ loop-shaping approach through non-diagonal weights

AbstractThis paper deals with the design methodology of multi-variable flight control systems through a H∞ loop-shaping technique. A new procedure for the design of non-diagonal pre-and post-compensators is described. In particular, important improvements over existing methods are introduced to both make the selection of weights easier and to contain the order of the resulting controller. The new procedure can be easily managed through suitable Matlab commands and functions, thus simplifying the whole algorithm implementation and providing an effective control system design with a minimum effort. Two typical design problems are addressed: a pitch pointing control system and a lateral controller for coordinated turns. In both cases, a good decoupling between existing channels is obtained by means of a non-diagonal pre-compensator which shapes the plant transfer function, and provides the desired response settling time. The design approach is particularly effective even for nominal plants with strong cross-coupling between channels. The design procedure is illustrated with the aid of a Matlab/Simulink model of a single seat fighter aircraft. We show that a trade-off between the conflicting requirements of fast response and moderate use of control surfaces can be easily managed by varying the constant terms of the diagonal post-compensator.

Active and passive vortex wake mitigation using control surfaces

Aircraft trailing vortices constitute a hazard to following aircraft and are therefore one of the main concerns for airport capacity constraints. At the Institute of Aerospace Engineering (ILR) experiments on wake vortices are conducted in a towing tank using particle image velocimetry. The motivation behind the presented investigations is the alleviation of the rolling moment induced on following aircraft using control surfaces of the preceding aircraft. An unstable vortex system is generated by the use of control surfaces. The instabilities lead to a mitigation of the vortex system. A variety of outboard flaps are used in preliminary studies to estimate the sizing and deflection of ailerons that lead to a vortex system with strong cooperative instabilities and thus to an alleviation of the rolling moment induced on following aircraft. In subsequent experiments a rectangular wing is equipped with preset ailerons, producing an unstable vortex system in its wake. The instabilities are excited by oscillating the ailerons. Each half-wing is equipped with two adjacent ailerons that oscillate in counter-phase in order to minimise fluctuations of the lift coefficient.

Computational Fluid Dynamics and Doublet-Lattice Calculation of Unsteady Control Surface Aerodynamics

Accurate prediction of control surface aerodynamics has been a challenge since the dawn of aviation. Whereas this has been an important problem for many years, recent increases in the use of control surfaces for active control (load alleviation and e utter suppression ) have increased the importance of accurate steady and unsteady control surface aerodynamics. Because of the strong ine uence of viscosity on the pressures on a trailing-edge control surface, the aerodynamic theories based on the linear potential equation have had only marginal success in predicting control surface aerodynamics, and in practice, large corrections (based on wind-tunnel data ) are often required for acceptable accuracy. Recent advances in computing technology and unsteady aerodynamic codes based on the Navier ‐Stokes equation areallowing moreaccurate analysesto be performed. Unsteady aerodynamic calculations due to control surface oscillations are made using a linear potential code (N5K) and a Navier‐Stokes code (CFL3D.AE-BA version 4.1 ). The Navier‐Stokes calculations are performed in the time domain using an exponential pulse technique and are transformed to the frequency domain using Fourier transform. For low reduced-frequency cases, theNavier ‐Stokes calculations arecompared to the doublet-lattice method and to experiment, and the advantages of the nonlinear analysis are clearly demonstrated. Correlation between Navier ‐Stokes and doublet-lattice results is then studied for higher reduced frequencies.