Date of Award

Summer 2008

Document Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Aerospace Engineering

Committee Chair

Darris White

Committee Member

R.R. Mankbadi

Committee Member

Charles F. Reinholtz

Committee Member

James Cunningham

Abstract

There have been several recent studies on the potential benefits of controllable dampers. Controllable dampers can use a fluid with controllable properties, such as Magneto - Rheological fluid (MR fluid), or control the damping force by changing orifice size. For this project, controllable dampers were created using MR fluid. When exposed to a magnetic fluid, the viscosity of MR fluid can change significantly. By replacing the standard damper oil in an aircraft landing gear and exposing the system to an appropriate magnetic field, the damping coefficients of the system can be changed almost instantaneously to accommodate nearly any situation. This trait allows a real time controller to monitor the system and adjust damping characteristics to match current conditions. Using the 'no-jerk' Skyhook control strategy, the control system attempts to minimize the acceleration, force and displacement transmitted to the fuselage from the ground. This reduction in applied load can translate into reduced aircraft weight, and longer fatigue life for some components. Unlike previous studies, the controllable damper configuration for this project used an externally mounted electromagnet located between the damper and remote reservoir, as opposed to an electromagnet located internal to the damper body. This design allows landing gear to use semi-active MR dampers with few modifications to existing designs. A set of dampers were tested in the standard and controllable configurations on a shock dynamometer. A SimMechanics model, which was calibrated using the dynamometer data and from limited 2-DOF experimental test data, was used to predict the improvement in transmissibility resulting from these modifications. The results indicate that controllable dampers using a ‘no jerk' skyhook control policy can reduce transmissibility of ground input to the fuselage.

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