1. STABILIZATION OF HELICOPTER SLING LOADS
Vefa Narli
Good afternoon everyone. Thank you for attending my presentation. My name is Vefa Narli. I am from DASL and my advisor and lab director is Professor Paul Oh. I am going to talk about our test-rig for near-Earth aerial robotics.

2. Introduction High Rise Rescue Fire Fighting Hover Offshore
Construction
Hover
Vertical Take-off and Land

3. Transportation Modes of Helicopters
23000 lbs
40000 lbs
5000 lbs

4. Helicopter Sling Loading Capacities
Reference
Helicopter
Weight
External Load
Load Mass
Ratio
Cable Length
3 ( Handling Qualities
Requirements for Military
Rotorcraft, Aeronautical Design
Standard) NA
0.33
4 (Requirements for the Certification of Sling Loaded Military Equipment for External Transportation by Department of Defense Helicopters )
39800 lbs (max)
12-16 ft 7
UH-60A
14600 lbs
lbs
23 ft (single)
15.83 ft -
(4-legged)
40000 lbs
3-140 ft 11
UH-60
16000 lbs
lbs ft
Superior Helicopter
Kaman
K-1200
12000 lbs
6000 lbs

5. Helicopter Sling Loading
Load is suspended beneath the helicopter
Free to rotate in all 3 axis
Long cable lines are used
Requires pilot effort

6. Literature Survey
Dukes, T. A., “Maneuvering Heavy Sling Loads Near Hover, Part I: Damping the Pendulous Motion,” Journal of the American Helicopter Society, Vol. 18, (2), Apr
Dukes, T. A., “Maneuvering Heavy Sling Loads Near Hover, Part II: Some Elementary Maneuvers,” Journal of the American Helicopter Society, Vol. 18, (3), July 1973.
Poli, C., and Cromack, D., “Dynamics of Slung Bodies Using a Single-Point Suspension System,” Journal of Aircraft, Vol. 10, (2), Feb
Cliff, E. M., and Bailey, D. B., “Dynamic Stability of a Translating Vehicle with a Simple Sling Load,” Journal of Aircraft, Vol. 12, (10), Oct
Nagabhushan, B. L., “Low-Speed Stability Characteristics of a Helicopter With a Sling Load,” Vertica, Vol. 9, 1985.
Sheldon, D. F., “An Appreciation of the Dynamic Problems Associated with the External Transportation of Loads from a Helicopter—State of the Art,” Vertica, Vol. 1, 1977.
Prabhakar, A., “Stability of a Helicopter Carrying an Underslung Load,” Vertica, Vol. 2, 1978.
Cicolani, L. S., Kanning, G., and Synnestvedt, R., “Simulation of the Dynamics of
Helicopter Slung Load Systems,” Journal of the American Helicopter Society, Vol. 40, (4), Oct
Gabel, R., and Wilson, G. J., “Test Approaches to External Sling Load Instabilities,” Journal of the American Helicopter Society, Vol. 13, (3), July 1968.

7. HSL Flight Tests
[7]

8. Stability of HSL - I
[7]

9. Stability of HSL - II
[7]

10. Stability of HSL - III [ 11]
Level 1 – Load maintains directional stability throughout the maneuvers. Minimal oscillation. Requires minimal concentration by the flight crew
Level 2 – Load may oscillate, rotate. Directional orientation is not stable. Does not pose a threat to the aircraft. ost maneuvers. Moderate oscillation.
[ 11]

11. Safety - I
Manwaring, J. C., Conway, G. A., Garrett, L. C., “Epidemiology and Prevention of Helicopter External Load Accidents,” Journal of Safety Research, Vol. 29, No. 2, pp , 1998.

12. Safety - II
…The helicopter departed with a 150-foot long-line attached and no external load on the hook… After lift-off, the long-line tangled in the trees, causing the helicopter to crash…
…An Aerospatiale 316B was moving equipment in mountainous terrain with a 100-foot long cable… the cargo hook snagged on an equipment trailer adjacent to the take-off area. As the tension on the line increased, the hook broke free of the trailer and the cable recoiled into the main rotor blades, rendering the helicopter uncontrollable…
…During the flight to reposition the helicopter that was transporting seismic equipment with a 100-foot long line, the load caught on a nearby fence…

13. Literature Survey
Lucassen, L. R., and Sterk, F. J., “Dynamic Stability Analysis of a Hovering Helicopter With A Sling Load,” Journal of the American Helicopter Society, Vol. 10, (2), Apr
(Dynamics and Stability)
Stiles et al, (2004, [22],) mention sling load active stabilization as a future direction of research in his review of Helicopter AFCS.

14. Statement of the Problem
Keep the oscillations of the payload under a critical angle, or deviation
The effect of the load on the helicopter dynamics should not exceed more than 10% of the static weight of the load.
System should be adjustable to different line length and load weight and should be robust to 10% changes of the nominal values.

15. Approach - I Modified AFCS that stabilizes the slung load
Stand-alone stabilizing system
Cartesian mechanism
Spherical mechanism

16. Approach - II
[2]
Cho, S.-K., Lee, H. H., “An Anti-Swing Control of a 3-Dimensional
Overhead Crane,” Proceedings of the American Control Conference, Chicago, Illinois,
pp , 2000.

17. Future Work Anti-sway control of shipboard boom cranes
Simulations of a quadrotor suspended mass
Update the statement of the problem
Stabilization of a 3D suspended pendulum with a cartesian mechanism
Stabilization of a 3D suspended pendulum with a spherical mechanism
UH-60 helicopter MatLAB model
Simulations of 3D suspended pendulum attached to UH-60

18. References
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Alleyne, A., Hedrick, J. K., “Nonlinear Adaptive Control of Active Suspensions,” IEEE Transactions on Control Systems Technology, Vol. 3, No. 1, pp , 1995, cited by 123.
Anonymous, “Handling Qualities Requirements for Military Rotorcraft, Aeronautical Design Standard,” ADS-33E-PRF, 2000.
Anonymous, “Requirements for the Certification of Sling Loaded Military Equipment for External Transportation by Department of Defense Helicopters”, MIL-STD-913A, 1997.
Balachandran B., Li, Y.-Y., Fang, C.-C., “A Mechanical Filter Concept For Control of Non-linear Crane-Load Oscillations”, Journal of Sound and Vibration, 228, pp , 1999, cited by 12.
Bartolini, G., Pisano, A., Usai, E., “Second-order Sliding-Mode Control of Container Cranes”, Automatica 38 pp , 2002, cited by 11.
Cicolani, L. S., Sahai, R., Tucker, G. E., McCoy, A. H., Tyson, P. H., Tischler, M. B., Rosen, A., “Flight Test Identification and Simulation of a UH-60A Helicopter and Slung Load”, NASA/TM , USAAMCOM-TR-01-A-001, 2001.
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Fusato, D., Guglieri, G., Celi, R., “Flight Dynamics of an Articulated Rotor Helicopter with an External Slung Load,” AHS International Annual Forum, 55th, Montreal, Canada, 1999, cited by 8.
Hrovat, D., “Survey of Advanced Suspension Developments and Related Optimal Control Applications,” Automatica, Vol. 33, No. 10, pp , 1997, cited by 121.
Karnopp, D., “Active Damping in Road Vehicle Suspension Systems,” Vehicle System Dynamics, 12, pp , 1983, cited by 50.
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Key, D. L., “Airworthiness Qualification Criteria for Rotorcraft With External Sling Loads”, NASA/TM , USAAMCOM AFDD/TR-02-A-002, 2002.
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Stiles, T. R., Mayo, J., Freisner, A. L., Landis, K. H., Kothmann, B. D., “Impossible To Resist, The Development of Rotorcraft Fly-by-Wire Technology,” AHS 60th Annual Forum, Baltimore, MD, 2004.
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