Smart helicopter rotor with piezoelectric bender actuated trailing-edge flaps

The main focus of this research is on the development of a Mach-scaled active rotor blade with trailing-edge flaps for vibration control. A solid state piezoelectric bender coupled with a rod-cusp single stage stroke amplifier is used to drive a plane trailing-edge flap that is completely integrated into the blade profile. Before embarking on the experimental test program, an analytic model was developed for the active rotor blade in hovering flight. The analysis involved the formulation of the coupled actuator-rotor equations of motion and their solution using a finite element method in space and time. The goal was to use this analysis in design studies and performance evaluation of the active rotor system.; The proof-of-concept study was extended to Mach-scale. A comprehensive aeroelastic rotor code (UMARC) was used to determine the optimal trailing-edge flap span, chord and spanwise location. This design study converged to a 8% span, 20% chord flap located at 75% spanwise location with associated flap deflection requirements of ±4 deg (at Mach-scaled operating speed of 1800 RPM).; The 4-bladed Mach-scaled model was tested in Hover at 1800 RPM (tip Mach number 0.45). Flap deflection amplitudes of ±4 to ±6 deg were achieved in the 1–5/rev frequency range at 1800 RPM. The open-loop hover tests also showed that the actuator-flap control authority increases dramatically when the trailing-edge flap excitation frequency is close to the blade flap-bending and torsion natural frequencies.; The 4-bladed Mach-scaled model was tested in the Glenn L. Martin wind tunnel to evaluate actuator-flap performance in forward flight. These tests consisted of open loop single frequency tests as well as closed loop vibration control tests conducted in conjunction with a neuro-controller. For the open-loop tests, the trailing-edge flap deflections ranged from ±4 to ±6 deg in the 1–5/rev frequency range and were quite insensitive to variations in the rotor collective pitch and advance ratio.; The objective of the closed loop tests in forward flight was to minimize multiple fixed frame 4/rev oscillatory loads (thrust, pitching moment and rolling moment). These tests were extremely successful, with up to 90% reduction in the oscillatory 4/rev thrust, pitching moment and rolling moment levels. (Abstract shortened by UMI.)...