STABILIZATION OF HELICOPTER SLING LOADS

1
STABILIZATION OF HELICOPTER SLING LOADS

• Vefa Narli

2
Introduction

• High Rise Rescue
• Fire Fighting
• 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 Helicopter Weight External Load Weight Load Mass Ratio Cable Length
3 ( Handling Qualities Requirements for Military Rotorcraft, Aeronautical Design Standard) NA NA NA 0.33 NA
4 (Requirements for the Certification of Sling Loaded Military Equipment for External Transportation by Department of Defense Helicopters ) NA NA 39800 lbs (max) NA 12-16 ft
7 UH-60A 14600 lbs 1130-6384 lbs 0.07-0.30 23 ft (single) 15.83 ft - (4-legged)
7 NA NA 40000 lbs NA 3-140 ft
11 UH-60 16000 lbs 1102-4409 lbs 0.06-0.22 9.84-26.2 ft
Superior Helicopter Kaman K-1200 12000 lbs 6000 lbs 0.33 NA
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. 1973.
• 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. 1973.
• 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. 1975.
• 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 HelicopterState
  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.
  1995.
• 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
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. 107-121, 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. 1965.
• - 2001 (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. 1037-1041, 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

1. Abdel-Rahman, E. M., Nayfeh, A. H., Masoud, Z.
   N., Dynamics and Control of Cranes A Review,
   Journal of Vibration and Control, 9, pp. 863-908,
   2003, cited by 15.
2. Alleyne, A., Hedrick, J. K., Nonlinear Adaptive
   Control of Active Suspensions, IEEE Transactions
   on Control Systems Technology, Vol. 3, No. 1, pp.
   94-101, 1995, cited by 123.
3. Anonymous, Handling Qualities Requirements for
   Military Rotorcraft, Aeronautical Design
   Standard, ADS-33E-PRF, 2000.
4. Anonymous, Requirements for the Certification of
   Sling Loaded Military Equipment for External
   Transportation by Department of Defense
   Helicopters, MIL-STD-913A, 1997.
5. 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. 651-682, 1999,
   cited by 12.
6. Bartolini, G., Pisano, A., Usai, E.,
   Second-order Sliding-Mode Control of Container
   Cranes, Automatica 38 pp. 1783-1790, 2002, cited
   by 11.
7. 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-2001-209619, USAAMCOM-TR-01-A-001, 2001.
8. Corriga, G., Giua, A., Usai, G, An Implicit
   Gain-Scheduling Controller for Cranes, IEEE
   Transactions on Control Systems Technology, Vol.
   6, No. 1, pp. 15-20, 1998, cited by 36.
9. Fang, Y, Dixon, W. E., Dawson, D. M., Zergeroglu,
   E., Nonlinear Coupling Control Laws For An
   Underactuated Overhead Crane System, IEEE/ASME
   Transactions on Mechatronics, Vol. 8, No. 3, pp.
   418-423, 2003.
10. Fliess, M., Levine, J., Rouchon, P., A
    Simplified Approach of Crane Control Via A
    Generalized State-Space Model, Proceedings of
    the 30th Conference on Decision and Control,
    England, pp. 736-741, 1991, cted by 29.
11. 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.
12. Hrovat, D., Survey of Advanced Suspension
    Developments and Related Optimal Control
    Applications, Automatica, Vol. 33, No. 10, pp.
    1781-1817, 1997, cited by 121.
13. Karnopp, D., Active Damping in Road Vehicle
    Suspension Systems, Vehicle System Dynamics, 12,
    pp. 291-316, 1983, cited by 50.
14. Karnopp, D., Design Principles for Vibration
    Control Systems Using Semi-Active Dampers,
    Journal of Dynamic Systems, Measurement and
    Control, Vol. 112, pp. 448-455, 1990, cited by
    43.
15. Key, D. L., Airworthiness Qualification Criteria
    for Rotorcraft With External Sling Loads,
    NASA/TM-2002-211390, USAAMCOM AFDD/TR-02-A-002,
    2002.
16. Kriikku, E., Singer, N., Singhose W., An Input
    Shaping Controller Enabling Cranes to Move
    Without Sway, American Nuclear Society 7th
    Topical Meeting on Robotics and Remote Systems,
    1997, cited by 36.
17. Kureemun, R., Walker, D. J., Manimala, B.,
    Voskuijl, M., Helicopter Flight Control Law
    Design Using Hinf Techniques, Proceedings of the
    44th IEEE Conference on Decision and Control, and
    the European Control Conference, pp. 1307-1312,
    2005.
18. Moustafa, K. A. F., Ebald, A. M., Nonlinear
    Modeling and Control of Overhead Crane Load
    Sway, Transactions of ASME, Vol. 110, pp.
    266-271, 1988, cited by 38.
19. Omar, H. M., Control of Gantry and Tower
    Cranes, PhD. Thesis, Blacksburg, Virginia, 2003,
    cited by 5.