Maneuvering Heavy Sling Loads Near Hover Part I: Damping the Pendulous Motion

Dukes, Theodor A.

doi:10.4050/jahs.18.2.2

Cited by 30 publications

(9 citation statements)

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“…A more effective solution consisted of an inner loop in which the relative motion of aircraft and load was fed back to cyclic, and an outer loop with the aircraft position fed back, again to cyclic. Dukes studied the basic stability characteristics of a helicopter with a slung load, possible feedback stabilization schemes [4], and appropriate piloting strategies for various maneuvers [5]. A 3-degree of freedom longitudinal helicopter/load model was used.…”

Section: Introductionmentioning

confidence: 99%

Flight Dynamics of an Articulated Rotor Helicopter with an External Slung Load

Fusato¹,

Guglieri²,

Celi³

2001

j am helicopter soc

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The paper presents a study of the flight dynamics of an articulated rotor helicopter carrying a suspended load. The aircraft model includes rigid body dynamics, individual flap and lag blade dynamics, and inflow dynamics. The load is a point mass with a single suspension point. Results were obtained for load masses of up to 2000 kg, with load-tohelicopter mass ratios of up to 28%, cable lengths from 3 to 8 m, turn rates of up to 16 deg/sec, and advance ratios of up to 0.3. The load affects trim primarily through the overall increase in the weight of the aircraft; the influence of cable length is negligible. Substantial coupling can occur between the Dutch roll and the load modes. Because of this coupling, the Dutch roll damping can decrease with a deterioration of handling qualities. The effects on the phugoid are very small. A suspended load modifies the roll frequency response by adding a notch to the gain curves and a 180-degree jump in the phase curves at the pendulum frequencies of the load. The changes in bandwidth and phase delay are small. Notation a L Absolute acceleration of the suspended load, Eq. (4). D Aerodynamic force vector acting on the load, Eq. (6). F H Force applied by the load to the helicopter, Eq. (8). f L Vector of load equations of motion, Eq. (7). i B , j B , k B Unit vectors of the body axis coordinate system (Figure 1). i G , j G , k G Unit vectors of the gravity axis system; the k G vector is directed along the vertical. i H , j H , k H Unit vectors of hook coordinate system (Figure 1). l Cable length. m Mass of the suspended load. n T Load factor. p, q, r Roll, pitch, and yaw rate of the helicopter. R H Position vector of the suspension point with respect to the aircraft CG, Eq. (2). R L Position vector of the load with respect to the suspension point, Eq. (1). S L Equivalent flat plate area of the suspended load. x H , y H , z H Components of the position vector of the suspension point with respect to the aircraft center of mass (Figure 1). Greek Symbols and Subscripts θ L , φ L Coordinates of the suspended load (Figure 1). θ F , φ F Pitch and roll angle of the fuselage. µ Advance ratio.

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Section: Introductionmentioning

confidence: 99%

Flight Dynamics of an Articulated Rotor Helicopter with an External Slung Load

Fusato¹,

Guglieri²,

Celi³

2001

j am helicopter soc

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“…. (11) The helicopter has three suspension points i = 1,2,3 underneath its floor as seen in Fig. A6, the tension force in one cable j being S ij .…”

Section: Appendix Amentioning

confidence: 99%

“…Searching in the specialist literature for papers on this particular area of load failures revealed that the subject has not been well investigated. The publications found are somewhat sparse, many of them relating only to the subject of modelling of the dynamics of a helicopter with a slung load (1)(2)(3)(4)(5)(6)(7) , the dynamic instabilities of a slung load (8)(9)(10)(11)(12)(13)(14)(15)(16)(17) , handling qualities of helicopter/slung load system (18)(19)(20)(21) or modelling the control system of a helicopter with a slung load (22,23) . A few publications have been identified dealing with load problems; however, they address mainly a rather different problem from that considered in the present paper, i.e.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Chinook helicopter operations with an external slung load after cable failure

Pavel¹

2010

Aeronaut. j.

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NOMENCLATURE a 0f , a 0r coning angle of front and rear rotor (rad) a 1f , a 1r longitudinal disc-tilt angles of front and rear rotors, positive when the rotor disc plane tilts backwards (rad) b 1f , b 1r lateral disc-tilt angles of front and rear rotor, positive when the disc plane tilts to the azimuth position ψ = 90˚ (rad)blade lift curve slope (rad -1 ) C Q rotor torque coefficient (-) C T,elem,f, C T,elem,r rotor thrust coefficients in blade element theory respectively for front and rear rotor (-) C T,Glau,f, C T,Glau,r rotor thrust coefficients in Glauert formulation respectively for front and rear rotor ( ABSTRACTThe Royal Netherlands Air Force (RNLAF) conducts frequent operations of Chinook helicopters with external slung loads. The normal RNLAF practice is for large external loads to be underslung by means of a two-strop suspension system backed up by a third point of suspension, the so-called 'redundant HUSLE (Helicopter Underslung Load Equipment)' comprising a redundant set of slings which come into action if one of the normal strops fails. The redundant HUSLE is relatively expensive in terms of time and operating costs. The present work has investigated the behaviour of a Chinook helicopter with an underslung load following failure of a front or rear strop, to determine whether the three-point suspension system can be safely replaced by a two-point suspension, eliminating the redundant HUSLE. The paper will demonstrate that although in general the redundant HUSLE results in a less violent helicopter reaction to a cable failure, it does not necessarily guarantee safety. It is concluded that flying with loads up to around two tonnes could be done safely with a two-point suspension system. A novel feature of this analysis of helicopter operations with slung loads is the integrated approach used for simulating pilot-in-the-loop load failures using a full non-linear model.

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“…Suspended load operations have long been studied for manned and unmanned systems. During the 1970s, assisting pilots by actively damping the carried load through specialized hardware [1][2][3] or feedback control [4][5][6][7] was the main focus of suspended load operations research. Recently, extensive piloted flight tests for a task-tailored control system with fuselage and cable angle/rate feedback has shown a significant reduction of load set-down time and a large improvement in average handling qualities [8,9].…”

Section: Introductionmentioning

confidence: 99%

Autonomous Suspended Load Operations via Trajectory Optimization and Variational Integrators

Torre

Theodorou

Johnson

2017

Journal of Guidance, Control, and Dynamics

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This paper present a real-time implementable trajectory optimization framework for autonomous suspended load operations in outdoor environments. The framework solves the posed optimal control problem with the iteration-based differential dynamic programming (DDP) algorithm. The algorithm utilizes a variational integrator to propagate the modeled system's state configuration and linearize the resulting discrete dynamics. It is shown that the variational integrator is an excellent candidate for real-time implementation since it remains accurate despite relatively large discretization time steps. Therefore, the computational effort of the DDP algorithm can be mitigated through the reduction of discrete time points. The state of the slung load is estimated via an augmentation to the existing navigation system that utilizes only vision-based measurements of the load. Simulation studies and a flight test are presented to demonstrate the effectiveness of the proposed framework. Nomenclature DG(Y) derivative of G(Y) with respect to Y D i G(Y 1 ,. .. , Y p) derivative of G(Y 1 , Y 2. .. , Y p) with respect to its i th argument, Y i G Y i (Y 1 ,. .. , Y p) derivative of G(Y 1 , Y 2. .. , Y p) with respect to Y i G Y i ,Y j (Y 1 ,. .. , Y p) second order mixed derivative of G(Y 1 , Y 2. .. , Y p) with respect to Y i and Y j

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Maneuvering Heavy Sling Loads Near Hover Part I: Damping the Pendulous Motion

Cited by 30 publications

References 0 publications

Flight Dynamics of an Articulated Rotor Helicopter with an External Slung Load

Flight Dynamics of an Articulated Rotor Helicopter with an External Slung Load

Investigation of Chinook helicopter operations with an external slung load after cable failure

Autonomous Suspended Load Operations via Trajectory Optimization and Variational Integrators

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