In the current work, the application and advantages of multiple active trailing-edge flaps for helicopter vibration control in forward flight are investigated. Small active flaps of this type can be actuated using smart materials. A comprehensive aeroelastic analysis is used to model a helicopter with multiple trailing-edge flaps. The objective function containing the hub vibratory loads and flap control effort is minimized by an optimal controller. The control effort is differentially weighted for different flaps, such that all trailing-edge flaps are exploited to their full authority and limited to ±2 degrees peak deflection. Numerical results are obtained for one, two and three flaps and their optimal locations identified. A reduction of 76% in the hub vibration level is achieved at an advance ratio (nondimensional forward speed) of 0.3 using three flaps. For the four-bladed, soft-inplane, hingeless rotor considered in this work, it is observed that the extent of hub vibration reduction is directly related to the effect of trailing-edge flap motion on the contribution of the second flapwise bending mode to blade motion. It is also shown that multiple flaps can effectively modify the participation of second flapwise bending mode at a much lower control power than is needed with single and dual flap configurations. Furthermore, multiple flaps are shown to allow redundancy in operation and are considerably more effective than single flaps in low speed transition flight regimes because of their capability in distributing the airloads.
Bernhard, A. and Chopra, I., 2001, "Analysis of a bending-torsion coupled actuator for a smart rotor with active blade tips," Smart Materials and Structures10(1), 35-52.
2.
Celi, R., 2003, "Stabilization of helicopter blades with severed pitch links using trailing-edge flaps," Journal of Guidance, Control and Dynamics26(4), 585-592.
3.
Centolanza, L.R., Smith, E.C., and Munsky, B., 2002, "Induced-shear piezoelectric actuators for rotor blade trailing edge flaps," Smart Materials and Structures11(1), 24-35.
4.
Chen, Y., Wickramasinghe, V., and Zimcik, D., 2005, "Smart spring impedance control algorithm for helicopter blade harmonic vibration suppression," Journal of Vibration and Control11(4), 543-560.
5.
Cribbs, R.C. and Friedmann, P.P., 2001, "Actuator saturation and its influence on vibration reduction by actively controlled flaps," in Proceedings of the 42nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, Seattle, WA, April 16-19, pp. 1-11.
6.
Dawson, S., Marcolini, M., Booth, E., Straub, F., Hassan, A., Tadghighi, H., and Kelly, H., 1995, "Wind tunnel test of an active flap rotor: BVI noise and vibration reduction," in Proceedings of the 51 st Annual Forum of the American Helicopter Society, Fort Worth, TX, May 9-11, pp. 631-648.
7.
Fink, D.A., Hawkey, T., Gaudreau, M., Wellman, B., and Ormiston, R., 2000, "An electromagnetic actuator for individual blade control ," in Proceedings of the 56th Annual Forum of the American Helicopter Society, Virginia Beach, VA, May 2-4.
8.
Friedmann, P.P., 1999, "The renaissance of aeroelasticity and its future," Journal of Aircraft36(1), 105-121.
9.
Friedmann, P.P., 2003, "Vibration reduction in rotorcraft using actively controlled flaps-from theoretical concept to flight ready hardware," in Proceedings of the Confederation of European Aerospace Societies /AIAA Joint International Forum on Structural Dynamics and Aeroelasticity , Amsterdam, The Netherlands, June 4-6, pp. 1-22.
10.
Friedmann, P.P. and Millott, T.A., 1995, "Vibration reduction in rotorcraft using active control: A comparison of various approaches," AIAA Journal of Guidance, Control and Dynamics18(4), 664-673.
11.
Friedmann, P.P., de Terlizzi, M., and Myrtle, T.F., 2001 "New developments in vibration reduction with actively controlled trailing edge flaps," Mathematical and Computer Modelling33(10-11), 1055-1083.
12.
Fulton, M.V. and Ormiston, R.A., 2001, "Hover testing of a small scale rotor with on-blade elevons ," Journal of the American Helicopter Society46(2), 96-106.
13.
Ganguli, R. and Chopra, I., 1996, "Aeroelastic optimization of helicopter rotor to reduce vibration and dynamic stresses," Journal of Aircraft12(4), 808-815.
14.
Hall, S.R. and Prechtl, E.F., 1996, "Development of a piezoelectric servoflap for helicopter rotor control," Smart Materials and Structures5(1), 26-34.
15.
Hariharan, N. and Leishman, J.G., 1996, "Unsteady aerodynamics of a flapped airfoil in subsonic flow by indicial concepts," Journal of Aircraft33(5), 855-868.
16.
Hodges, D.H. and Dowell, E.H., 1974, "Nonlinear equations of motion for the elastic Bending and torsion of twisted nonuniform rotor blades," NASA TN D-7818, NASA, Washington, DC.
17.
Johnson, W., 1982, "Self-tuning regulators for multicyclic control of helicopter vibration," NASA-TP-1996, NASA, Washington, DC.
18.
Kim, J.S., Smith, E.C., and Wang, K.W., 2004, "Helicopter vibration suppression via multiple trailing edge flaps controlled by resonance actuation system," in Proceedings of the 60th Annual Forum of the American Helicopter Society, Baltimore, MD, June 7-10, pp. 1611-1622.
19.
Koratkar, N. and Chopra, I., "Closed-loop wind tunnel testing of a smart rotor model with trailing-edge flaps," Journal of the American Helicopter Society47(4), 263-272.
20.
Kunze, O., Arnold, U.T.P., and Waaske, S., 1999, "Development and design of an individual blade control system for the Sikorsky CH-53G helicopter," in Proceedings of the 55th Annual Forum of the American Helicopter Society, Montreal, Quebec, Canada, May 25-27.
21.
Lee, T. and Chopra, I., 2001, "Design of piezostack-driven trailing edge flap actuator for helicopter rotors," Smart Materials and Structures10(1), 15-24.
22.
Lim, S., Park, S., and Kim, K., 2005, "AI vibration control of high-speed rotor systems using electrorheological fluid," Journal of Sound and Vibration284(3-5), 685-703.
23.
Milgram, J. and Chopra, I., 1998, "A parametric design study for actively controlled trailing edge flaps," Journal of the American Helicopter Society43(2), 110-119.
24.
Milgram, J., Chopra, I., and Straub, F., 1998, "Rotors with trailing edge flaps: Analysis and comparison with experimental data," Journal of the American Helicopter Society43(4), 319-332.
25.
Myrtle, T.F. and Friedmann, P.P., 2001, "Application of a new compressible time domain aerodynamic model to vibration reduction in helicopters using an actively controlled flap ," Journal of the American Helicopter Society46(1), 32-43.
26.
Nguyen, K. and Chopra, I., 1990, "Application of higher harmonic control to rotor operating at high speed and thrust," Journal of American Helicopter Society35(3), 336-342.
27.
Ormiston, R.A., 2001, "Aeroelastic considerations for rotorcraft primary control with on-blade elevons," in Proceedings of the 57th Annual Forum of the American Helicopter Society, Washington DC, 2001, pp. 464-481.
28.
Patt, D., Liu, L., and Friedmann, P.P., 2005, "Rotorcraft vibration reduction and noise prediction using a unified aeroelastic response simulation," Journal of the American Helicopter Society50(1), 95-106.
29.
Shen, J. and Chopra, I., 2004, "Swashplateless helicopter rotor with trailing-edge flaps ," Journal of Aircraft41(2), 208-214.
30.
Spencer, M.G., Sanner, R.M., and Chopra, I., 1999, "Adaptive neurocontrol of simulated rotor vibrations using trailing edge flaps," Journal of Intelligent Material Systems and Structures10(11), 855-871.
31.
Straub, F.K. and Charles, B.D., 2001, "Aeroelastic analysis of rotors with trailing edge flaps using comprehensive codes," Journal of the American Helicopter Society46(3), 192-199.
32.
Viswamurthy, S.R. and Ganguli, R., 2004, "An optimization approach to vibration reduction in helicopter rotors with multiple active trailing edge flaps," Aerospace Science and Technology8(3), 185-194.
33.
Wang, J. and Meng, G., 2005, "Study of the vibration control of a rotor system using a magnetorheological fluid damper," Journal of Vibration and Control11(2), 263-276.
34.
Wilbur, M.L., Mirick, P.H., Yeager, W.T., Langston, C.W., Cesnik, C.E.S., and Shin, S., 2002, "Vibratory loads reduction testing of the NASA/Army/MIT active twist rotor," Journal of the American Helicopter Society47(2), 123-133.
35.
Wood, E.R., Powers, R.W., Cline, C.H., and Hammond, C.E., 1985 "On developing and flight testing a higher harmonic control system," Journal of American Helicopter Society30(2), 1-20.
36.
Zhang, J.H., Smith, E.C., and Wang, K.W., 2004, "Active-passive hybrid optimization of rotor blades with trailing edge flaps," Journal of the American Helicopter Society49(1), 54-65.
37.
Zhu, C., "A disk-type magneto-rheological fluid damper for rotor system vibration control," Journal of Sound and Vibration283(3-5), 1051-1069.
