Equilibrium characteristics and stability analysis of helicopter slung-load system

Abstract

Based on rigid-body slung-load hypothesis, a nonlinear dynamical model of the helicopter and slung-load system is presented. As for helicopter and slung-load system, the introduction of the rigid-body slung-load results in several extra degrees of freedom and constraints, and this makes the nonlinear equations of helicopter and slung-load motion transfer from 9 orders to 19 orders. The nonlinear equations are linearized by small perturbation hypothesis for stability analysis and they are trimmed by the continuation method. First, the simulation trimmed results are compared with the helicopter flight test data without slung-load and the calculation results of helicopter with mass-point slung-load in the literature. Then, the differences among trimmed states of the helicopter with a rigid-body slung-load, a mass-point slung-load, and without slung-load are studied. The motion modes of helicopter with rigid-body slung-load are calculated in different cases, and the effects of extra slung-load to the helicopter stability are analyzed at the same time. Results showed that the rigid-body slung-load added five new motion modes to the whole helicopter and slung-load system, two of which concerning cable swinging motion are stable, while the others concerning slung-load attitude motion are unstable. At the same time, the introduction of rigid-body slung-load makes the short-period mode and the roll mode of helicopter unstable, which has a strong impact on the flight quality of helicopter.

Keywords

Helicopter rigid-body slung-load trim stability mode

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References

Wolkovitch J, Johnston D, et al. Automatic control considerations for helicopter and VTOL aircraft with and without sling loads. Technical Report 138-1, Systems Technology Inc., 1965.

Polit

Cromack

. Dynamics of slung bodies using a single-point suspension system. J Aircraft 1973; 10: 80–86.

Micale

Polit

. Dynamics of slung bodies utilizing a rotating wheel for stability. J Aircraft 1973; 10: 760–763.

Gera

Farmer

. A method of automatically stabilizing helicopter sling loads 1974; vol. 7593, Washington, DC, US: NASA.

Sampath

. Dynamics of a helicopter-slung load system, Maryland, US: University of Maryland, 1980.

Nagabhushan B and Cliff E. Maneuver stability of a vehicle with a towed body. In: 9th Conference of atmospheric flight mechanics, San Diego, CA, 9–11 August, 1982. New York, NY: American Institute of Aeronautics and Astronautics.

Nagabhushan

. Low-speed stability characteristics of a helicopter with a sling load. Vertica 1985; 9: 345–361.

Ronen

. Dynamics of a helicopter with a sling load, Stanford: Stanford University, 1986.

Reddy KR, Truong TT, Stuckey RA, et al. Dynamic simulation of a helicopter carrying a slung load. International Congress on Modelling and Simulation, 2007, pp.2740–2746.

10.

Cicolani

Kanning

Synnestvedt

. Simulation of the dynamics of helicopter slung load systems. J Am Heli Soc 1995; 40: 44–61.

11.

Fusato

Guglieri

Celi

. Flight dynamics of an articulated rotor helicopter with an external slung load. J Am Heli Soc 2001; 46: 3–13.

12.

Bisgard

. Modeling, estimation, and control of helicopter slung load system, Copenhagen, Denmark: Aalborg University, 2007.

13.

Bisgaard M, Cour-harbo A and Bendtsen JD. Full state estimation for helicopter slung load system. In: AIAA guidance, navigation, and control conference and exhibit, 20–23 August 2007, pp.1–15. Hilton Head, US: AIAA Guidance, Navigation and Control Conference.

14.

Luigi

Andrew

Johannes

. Flight Test and simulation of a cargo container slung load in forward flight. J Am Heli Soc 2009; 54: 1–18.

15.

Sumant S, Narayanan K, Marilyn S, et al. Aerodynamic instability modes for a load slung from a helicopter. In: Proceedings of the ASME 2012 international mechanical engineering congress & exposition, Houston, Texas, USA, 9–15 November, 2012.

16.

Tugrul

Cornel

. Modeling and control of a helicopter slung-load system. Aerosp Sci Technol 2013; 29: 206–222.

17.

Ronen

Bryson

Hindson

. Dynamics of a helicopter with a sling load. AIAA Atmos Flight Mech Confer 1986; 86-2288-CP: 1–13.

18.

Sturgeon WR. A mathematical model of the CH-53 helicopter. NASA TN-D-81238, 1980.

19.

Georgene L and Hifu K. Wind tunnel investigation of aerodynamic characteristics of scale models of three rectangular shaped cargo containers. NASA TM-X-62169, 1972.

20.

Heffley RK, Jewell WF, Lehman JM, et al. A compilation and analysis of helicopter handling qualities data, volume one: data compilation. NASA-CR-3144, 19.