Parafoil Control Authority with Upper-Surface Canopy Spoilers

Gavrilovski, Alek; Ward, Michael B.; Costello, Mark

doi:10.2514/1.c031685

Cited by 21 publications

(7 citation statements)

References 12 publications

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“…Note that the upper-surface bleed air opening is located at approximately 0.25c back from the leading edge, where c represents the mean airfoil chord. This configuration is similar to that tested by Gavrilovski et al in [1].…”

Section: Test Vehicle Descriptionsupporting

confidence: 89%

“…In contrast with asymmetric brake deflection, symmetric brake deflection predominantly causes a reduction in forward flight speed, with small changes in system glide slope until stall [1]. Although these systems have demonstrated substantial improvement in landing accuracy over similarly sized unguided systems, their limited number of available control channels and the effectiveness and independence of each control channel makes them highly susceptible to atmospheric gusts and other unknown surface conditions.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, several researchers have demonstrated that adding longitudinal or glide slope control is a very effective means for reducing impact point errors and can greatly improve landing accuracy [2][3][4][5]. Several mechanisms capable of effective glide slope control have been identified, including symmetric brake deflection for airspeed control [2], in-flight adjustment of the canopy incidence angle [3,4,6], and actuation of upper-surface bleed air spoilers [1,7]. This latter mechanism is the subject of the current work and consists of several spanwise slits in the upper surface of the parafoil canopy that, when opened, create a virtual spoiler by releasing pressurized air from within the canopy cell.…”

Section: Introductionmentioning

confidence: 99%

“…Much like conventional aircraft spoilers, opening of these spanwise slits creates a disturbance in the airflow over the parafoil wing, resulting in a localized perturbation of the associated aerodynamic forces. By varying the location of these slits along the upper surface of the canopy, significant changes in the lateral and longitudinal dynamics of the vehicle are achieved [1].…”

Section: Introductionmentioning

confidence: 99%

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Combined Lateral and Longitudinal Control of Parafoils Using Upper-Surface Canopy Spoilers

Scheuermann

Ward

Cacan

et al. 2015

Journal of Guidance, Control, and Dynamics

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Precision placement of guided airdrop systems necessarily requires some mechanism enabling effective directional control of the vehicle. Often this mechanism is realized through asymmetric deflection of the parafoil canopy trailingedge brakes. In contrast to conventional trailing-edge deflection used primarily for lateral steering, upper-surface bleed air spoilers have been shown to be extremely effective for both lateral and longitudinal (i.e., glide slope) control of parafoil and payload systems. Bleed air spoilers operate by opening and closing several spanwise slits in the upper surface of the parafoil canopy, thus creating a virtual spoiler from the stream of expelled ram air. The work reported here considers the autonomous landing performance of a small-scale parafoil and payload system using upper-surface bleed air spoilers exclusively for both lateral steering and glide slope control. Landing accuracy statistics computed from a series of Monte Carlo simulations in a variety of atmospheric conditions and experimental flight tests were found to be in good agreement. Median miss distances for the combined lateral and longitudinal control logic are on the order of 13 m, indicating an improvement in landing accuracy of nearly 50% over similar systems employing only lateral steering control. Nomenclature F = vehicle turn rate mapping GS min , GS max = minimum and maximum system glide slope GS c = commanded system glide slope H = system glide slope mapping h = current altitude, m I I , J I = inertial reference frame axes along the north and east directions I wf , J wf = wind-fixed reference frame axes along the downwind and crosswind directions L = instantaneous distance from target, m R = turn radius, m V 0 = estimated horizontal projection of vehicle airspeed, m∕ŝ V W;x ,V W;y = estimated wind velocity components along inertial north and east directions, m∕s x, y = inertial position components of system mass center, m x T , y T = target coordinates, m x wf , y wf = wind-fixed components of system mass center, m _ z = system sink rate, m∕s α = aerodynamic angle of attack, rad β = sideslip angle, rad δa, δs = asymmetric, symmetric spoiler deflection δl, δr = left, right spoiler deflection χ 0 = system total velocity azimuthal angle, rad ψ = system heading angle, rad ψ c = commanded system heading angle, rad ψ W = wind direction, rad

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Section: Test Vehicle Descriptionsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Combined Lateral and Longitudinal Control of Parafoils Using Upper-Surface Canopy Spoilers

Scheuermann

Ward

Cacan

et al. 2015

Journal of Guidance, Control, and Dynamics

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show abstract

“…These personnel systems used a combination of coupled control lines (trailing-edge deflection and spoilers) where the bleed air vents opened and closed to spoil the flow across the upper surface of the parachute. Higgins [13] documented the potential use of a bleed air vent system for autonomously controlled airdrop systems, and Gavrilovski et al [14] used a virtual spoiler method on a non-airdrop ram-air gliding system for both lateral and longitudinal control. Flight tests of the method [15] showed a linear glideslope change with respect to spoiler deflection and a linear dependence between the number of cells activated and the percent of glideslope change.…”

mentioning

confidence: 99%

Prediction of Aerodynamic Characteristics of Ram-Air Parachutes

Ghoreyshi

Bergeron

Seidel

et al. 2016

Journal of Aircraft

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The focus of this work is on the computational methodology for aerodynamic modeling of ram-air parachutes and increasing confidence and understanding in their concept designs including new parachute control methods. The complex geometries of ram-air parachutes are modeled by two-dimensional rigid airfoil geometries with or without trailing-edge deflections and bleed air spoilers. The aerodynamic forces are then calculated from steady or unsteady Reynolds-averaged Navier-Stokes simulations using Cobalt and Kestrel flow solvers. The effects of the grid size and type, the time step, and the choice of solver parameters are investigated. The flow solvers are then used to study the flow around three-dimensional wings with open/closed ram-air inlets by comparing lift and drag coefficients with available experimental data. The results show that computational fluid dynamics simulations are a valuable aid in understanding the flow structure of ram-air parachutes, which resemble a rectangular wing with open inlets. However, the computational solutions of these geometries have initial oscillations of large amplitude and converge slowly compared to closed wings/airfoils. The simulation of open geometry should run unsteady and for a large number of time steps. It is also shown that an open-inlet geometry has smaller lift and larger drag, and it stalls earlier than a closed-inlet geometry. Although the air reaches stagnation conditions inside the cavity present in an open airfoil, the air pressure inside the wing cells is less than the stagnation pressure. The flow investigations show that eddies are formed on the lower surface of the open airfoil and wings; however, the wing eddy size varies in the spanwise direction. Finally, the grid sensitivity results show that the solutions of open geometries are very sensitive to the grid quality. Nomenclature a = acoustic speed, m∕s b = wingspan, m C D = drag coefficient; D∕q ∞ ⋅ S C L = lift coefficient; L∕q ∞ ⋅ S c = airfoil/wing chord, m D = drag force, N F Z = normal force, N h = inlet length, m L = lift force, N M = Mach number, V∕a q ∞ = dynamic pressure, Pa Re = Reynolds number, ρVc∕μ S = reference area, m 2 t = time, s t = nondimensional time step, Vt∕c V = velocity, m∕s x, y, z = grid coordinates, m α = angle of attack, rad μ = air viscosity ρ = density, kg∕m 3

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Real-Time Data Acquisition and Model Identification for Powered Parafoil UAV

Lin

et al. 2015

Intelligent Robotics and Applications

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Parafoil Control Authority with Upper-Surface Canopy Spoilers

Cited by 21 publications

References 12 publications

Combined Lateral and Longitudinal Control of Parafoils Using Upper-Surface Canopy Spoilers

Combined Lateral and Longitudinal Control of Parafoils Using Upper-Surface Canopy Spoilers

Prediction of Aerodynamic Characteristics of Ram-Air Parachutes

Real-Time Data Acquisition and Model Identification for Powered Parafoil UAV

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