DESIGN OF A CENTRIFUGE AND AERODYNAMIC TESTING APPARATUS FOR EVALUATING THE PERFORMANCE OF A NOVEL TRAILING-EDGE FLAP ACTUATOR

Open Access
Author:
Cormier, Christopher
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Eric M Mockensturm, Thesis Advisor
Keywords:
  • individual blade control
  • centrifuge
  • smart materials
  • rotorcraft
Abstract:
Primary helicopter flight control generally involves exposed, high-maintenance equipment such as bearings, linkages, hinges, and swashplates. Though these mechanisms are necessary for helicopter flight performance, they are also a significant source of aerodynamic drag. Even though the status quo for vertical lift rotorcraft was set in the 1930's with the invention of the cyclic pitch controlling swashplate, this design has served admirably well for over 70 years. Unfortunately, swashplate failures have been shown to be a contributing cause of fatal helicopter accidents, prompting investigation into modern replacements for a decades-old technology. To date, many proposed swashplate replacement technologies have been studied, including blade camber control, blade twist control, tilting shaft concepts, active servo flaps, and active trailing edge flaps. Performance gains differ in every case, but active trailing-edge flaps have been proved effective in both noise and directional flight control. Additionally, trailing edge flap performance benchmarks have been set by The Boeing Company, using the double X-frame actuator. A new alternative to the double X-frame actuator, developed by Invercon LLC, promises an improved torque to weight ratio. As opposed to using levers and elastic hinges to amplify the motion of piezoelectric stacks, as with the X-frame system, this next-generation flap actuator utilizes an elastically buckled element to efficiently convert piezoelectric linear displacement into high torque flap rotation. To make a fair comparison to the double X-frame actuator, the author has split the performance into two categories: robustness to centrifugal loads, and authority over aerodynamic loads. Boeing recently tested the double X-frame and trailing edge flap system in a MD-900 bearingless helicopter rotor. Using this test as a benchmark, Invercon's actuator must be robust enough to maintain performance at steady-state centrifugal accelerations of 655g. Additionally, the actuator must have authority over aerodynamic and frictional loads on the trailing edge flap, estimated to be as high as +/-25 in-lbs torque at +/-3.5 degrees flap deflection.