Design Issues of a High-Stroke, On-Blade Piezostack Actuator for a Helicopter Rotor with Trailing-Edge Flaps

A compact actuator to oscillate blade trailing-edge flap on a full-scale helicopter has been investigated for vibration suppression. The actuator consists of piezoelectric stacks and a dual-stage mechanical stroke amplifier. It is recommended that commercially available piezostack be used for timely manufacturing and maintenance rather than a custom-designed piezostack. An analytical approach to estimate the maximum actuator force requirement for the rotor in hover condition is discussed first. A piezostack down-selection through the experimental evaluation is presented, which is to select a piezostack with high stiffness as well as good strain/block force output among twelve commercial piezostacks. The design requirements of on-blade piezoelectric actuator are discussed, and one-dimensional stiffness modeling and finite element beam modeling are presented to evaluate the analytical/numerical actuator performance. The prototype actuator with a double-lever stroke amplifier was fabricated and tested on bench-top as well as in vacuum chamber. An amplification factor of 19.4 and the consistent actuator output up to 600 g of centrifugal loading were obtained. An improved actuator has been designed with a design refinement to reduce structural losses.