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Title:Assessment of moving-mass actuators for hypersonic vehicles with deployable decelerators
Author(s):Lohan, Kevin George
Advisor(s):Putnam, Zachary R
Department / Program:Aerospace Engineering
Discipline:Aerospace Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:M.S.
Genre:Thesis
Subject(s):Moving-mass
control
Abstract:This study assesses internal moving-mass actuator configuration options for trajectory control in the hypersonic regime of planetary entry. Trajectory control is achieved by shifting the location of the center of gravity relative to the center of pressure to modify aerodynamic trim conditions. The vehicle is modeled as a cylinder with a deployable forebody and a moving-mass actuator that can translate along a linear track. Placing the track in the rear of the vehicle can reduce the required actuator mass fraction for a specific trim lift-to-drag ratio by up to 5%. Increasing the length of the track similarly reduces required mass fraction. Vehicle packaging density and size do not significantly influence the required actuator mass; geometric properties such as length-to-diameter ratio and the diameter of the deployable impact the required actuator mass. Using these design guidelines, and actuator mass fraction of approximately 13% is required to achieve a maximum lift-to-drag ration similar to the Mars Science Laboratory. A range of expected hypersonic flight conditions are analyzed to determine their impact on the achievable lift-to-drag ratio. For a moving-mass actuator mass fraction of 1%, the available lift-to-drag ratio varies between 0.02 and 0.06; for a 5% mass fraction the available lift-to-drag ratio varies between 0.1 to 0.13. A study of the system response is presented across vehicle geometries, and mass motions. A preliminary closed-loop PD control is presented which reduces the 2% settling time from 9 seconds to 5 seconds and removes all oscillations. An optimal control formulation is then solved, to minimize time, which reduces the settling time from 5 seconds to 0.6 seconds. The optimal control solutions move the mass primarily in the z direction, and adding a vertical constraint to the problem only marginally increases the settling time.
Issue Date:2017-04-28
Type:Thesis
URI:http://hdl.handle.net/2142/97505
Rights Information:Copyright 2017 Kevin Lohan
Date Available in IDEALS:2017-08-10
Date Deposited:2017-05


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