A COMPARISON OF HELICOPTER ACTIVE ROTOR GUST REJECTION AND VIBRATION ALLEVIATION METHODS

Open Access
Author:
Corl, Jonas Daniel
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Christopher Rahn, Thesis Advisor
  • Edward C Smith, Thesis Advisor
  • Stephen Clarke Conlon, Thesis Advisor
Keywords:
  • helicopter
  • swashplate
  • active rotor
Abstract:
Dynamic Interface (DI) tasks such as station keeping, takeoff, and landing during helicopter-ship interactions are often unacceptably workload-intensive due not only to close quarters and a rolling ship, but also to a gusty environment that is amplified by ship superstructure. Previous research has focused on creating controllers with the ship’s airwake properties included in the synthesis in order to compensate for gusts without affecting pilot commands. These controllers alleviate gusts using either the standard swashplate-based control or using trailing-edge flaps (TEFs) but both methods show similar performance. This study investigates the effects of both controllers on the requirements of the swashplate actuators. A nonlinear inverse kinematic and dynamic model of the swashplate mechanism is developed that relates the blade pitching motions to actuator and pitch link motions and forces. Results from simulations of a UH-60 Blackhawk landing on an LHA class ship in various airwakes are input into the swashplate model to determine the motion and forces required of the actuators. The controllers are compared with regard to their relative impact on component wear and fatigue. Trailing edge flap based gust alleviation is shown to reduce the total actuator cumulative travel by 31% and the number of direction reversals in a single actuator by 38%. Helicopter vibrations can exacerbate the effects of high workload environments by increasing pilot fatigue and causing back pain during long missions. Previous work has shown that active rotors equipped with trailing edge flaps are able to significantly reduce helicopter vibrations at the rotor hub and pilot seat. Trailing edge flap and root pitch methods of active rotor vibration control from previous studies are compared in terms of vibration reduction capabilities and required actuation force, power, and weight. Root pitch control and trailing edge flaps show closed loop multi-axis vibration reductions of 84% and 90%, respectively. Trailing edge flaps are found to be the most desirable due to low actuation power requirements. Current actuation technology, however, is not sufficient for trailing edge flaps on heavy helicopters, whereas root pitch actuation has been successfully demonstrated.