Terfenol-D driven flaps for helicopter vibration reduction

Abstract

The utility of helicopter aviation is limited by the high vibration levels caused by the interaction of each rotor blade with the wake of preceding blades. Existing full-blade actuation using a swashplate has various problems such as insufficient bandwidth, limitations in the number of harmonics controlled, high maintenance, and lack of spanwise lift variation. These problems are avoided by the proposed flap operated, individual blade control system, which uses magnetostrictive actuation technology. Terfenol-D actuation has many advantages over competing technologies such as hydraulic systems, electric motors, and piezoelectric elements. These benefits include all-electric operation, simplicity and reliability, low mass, low voltage, and insensitivity to centripetal acceleration. A blade mounted Terfenol-D actuator was developed for the high-weight-penalty helicopter application. The optimum coil to Terfenol-D volume ratio was derived that gives the highest mechanical power output for a small actuator envelope and mass. A fixed ability to dissipate coil resistive losses is assumed. The magnetostrictive actuation system will weigh less than 1% of gross vehicle weight, and use only 0.7% of cruise power. Other required subsystems of the vibration reduction system are available from commercial sources or are described in the literature. Helicopter vibration reduction greater than 90% is predicted because of superior actuator performance and individual blade control. This magnetostrictive actuator technology will also produce future helicopter systems having lower noise and higher performance. Such advances will significantly improve the utility and competitiveness of helicopters for civilian and military transportation.

Design and testing of a double X-frame piezoelectric actuator

“…[ : I (15) The stiffness matrix of the assembled double X-frame is given by k11 k12 0 = k21 2k22 k12 (16) 0 k22 k12…”

Engineering Feasibility of Induced Strain Actuators for Rotor Blade Active Vibration Control

“…Another study was independently conducted by SatCon Technology Co. in cooperation with MIT (Fenn, Downer, Bushko, Gondhalekar, and Ham, 1993). The design of a TERFENOL-D driven, servo-flap for Sikorsky UH-60A Black Hawk helicopter rotor blade was considered.…”

“…Basic Requirements for Rotor Blade HHC: Force, Displacement and Frequency It is generally accepted (Fenn, Downer, Bushko, Gondhalekar, and Ham, 1993;Straub and Charles, 1990;Samak and Chopra, 1993) that at least t 2 of oscillatory blade pitch at (4 t 1)/rev frequencies (approximately 25 t 5 Hz) is required to achieve significant vibration reduction via HHC-IBC. When using servo-flap actuation, this value must be transformed into an equivalent servo-flap amplitude.…”

“…As a means of vibration control, the IBC implementation of the HHC concept can address the vibrations due to manufacturing variability between the blades, and also is not restricted by the N + 1, N -1 phenomenon specific to swash plate considerable control force is required. For example, Fenn, Downer, Bushko, Gondhalekar, and Ham (1993) estimated the aerodynamic pitch moment for root actuation in the range 450-780 Nm. Another, more efficient way of individual blade control is to utilize the principle of servoaerodynamic, i.e., to take energy from the airstream and use it to modify the blade pitch.…”

Full-field infrared phase sensitive thermography for microstructural investigation of giant magnetostrictive materials

“…This material is unique for its huge magnetostriction compared to other materials, such as Galfenol or nickel. This unique property has also led many proposals for its applications in actuation and energy harvesting (Ashley 1998;Goodfriend and Shoop 1992;Fenn et al 1996). Magnetostriction can be attributed to the rotation of the magnetic moments for the alignment with the external magnetic field direction (Engdahl 2000).…”