Development and validation of a refined piezostack-actuated trailing edge flap actuator for a helicopter rotor

A methodology to develop piezostack-based actuator for trailing edge flap on a full-scale helicopter rotor blade is presented. By a systematic down-selection approach through the experimental validation on piezostack characteristics, one among numerous candidates was chosen for current study, which has higher stiffness as well as good strain/block force capability. The prototype actuator was designed and fabricated using two pieces of selected piezostack incorporated with a double-lever amplification mechanism that extends a lever-fulcrum amplification concept. To validate the feasibility of the designed actuator,the prototype actuator was tested in vacuum chamber that simulates the centrifugal force environment. It was shown that the actuator operated with no major degradation in performance up to 600g of centrifugal loading. The present actuator has a capability of oscillating the trailing edge flap to the required deflection/frequency to actively control rotor vibration in the rotating environment. Then, a further design refinement was considered to reduce the drawbacks, which finally results in an improved actuator with peak actuation force of 80 lbs at 38 mils stroke.