Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 26 for “"reaction wheels"”.
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Analysis, Simulation, and Measurement of Micro-Vibrations in Reaction Wheels for High-Performance Imaging Missions
… degraded by micro-vibrations originating from reaction wheels, which are the primary attitude actuators. These vibrations, resulting from mechanical unbalance, torque ripple, and bearing imperfections, propagate through the satellite structure and induce line-of-sight (LoS) jitter. This thesis …
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An attitude determination and control system for small satellites
… Using commercial-off-the-shelf sensors, reaction wheels, and magnetorquers which fit within the 3U CubeSat form factor, the system delivers arc-minute pointing precision. The ADC system includes a multiplicative extended Kalman filter for attitude determination and a slew rate controller …
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A fluid loop actuator for active spacecraft attitude control - A Parametric Sizing Model and the Design, Verification, Validation and Test with a Prototype on an Air Bearing
… the inertial mass has potential advantages over reaction wheels, including high torque, lower power consumption, reduced jitter and prolonged lifetime. Previous work addressed conceptual and mission-specific control aspects, and one fluid loop has flown on a demonstration mission. In this …
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FILM EVAPORATION MEMS THRUSTER ARRAY FOR MICROPROPULSION
… systems which are either quickly saturated reaction wheels or movable high drag surfaces with long response times. What is needed is a low mass low power self-contained propulsion unit that can be easily installed and modeled.
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Electromagnetic formation flight dipole solution planning
… concept of using electromagnets (coupled with reaction wheels) to provide all of the necessary forces and torques needed to maintain a satellite's relative position and attitude in a formation of satellites. With EMFF, this formation can be controlled without the use of traditional thrusters. …
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High-precision pointing and attitude estimation and control algorithms for hardware-constrained spacecraft
… accomplished through a two-stage control system: reaction wheels for coarse attitude control and a piezo stage for fine pointing control. A linear analysis developed using stochastic linearization techniques is used to analyze the various contributions to pointing error, allowing software …
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Adaptive Control Applied to the Cal Poly Spacecraft Attitude Dynamics Simulator
… bearing spacecraft simulator controlled by four reaction wheels in a pyramidal arrangement. Tests were performed to determine the effectiveness of the two adaptive control theories under nominal operating conditions, a “plug-and-play” spacecraft scenario, and under simulated actuator damage. …
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An Autonomous Underwater Vehicle for Validating Internal Actuator Control Strategies
… is provided by three orthogonally mounted reaction wheels. The housing is a spherical glass pressure vessel, which contains all of the components, such as actuators, ballast system, power supply, on-board computer and inertial sensor. Since the housing is spherically symmetric, the …
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A Comparison of PID and Sliding Mode Controllers When Applied to the Orbit Raising of a Satellite Using Solar Sail Propulsion
… of commonly used control actuators, specifically reaction wheels, when applied to solar sails. This thesis will research how a sliding mode controller compares to a PID controller with respect to settling time and state response error over a range of maximum reaction wheel torque values. The …
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Electromagnetic formation flight of satellite arrays
… in sparse aperture arrays use propellant as a reaction mass. For formation flying systems, propellant becomes a critical consumable which can be quickly exhausted while maintaining relative orientation. Furthermore, the total required propellant mass is highly dependant on [delta]V, which …
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Design, analysis, and testing of a precision guidance, navigation, and control system for a dual-spinning Cubesat
… add gyroscopic stiffness. An orthogonal triple reaction wheel assembly from Maryland Aerospace, Inc., will both counter the angular momentum from the payload and rotate the satellite's bus about its orbit-normal vector to maintain bus alignment with the orbital frame. The payload spins about the …
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Investigation of Nonlinear Control Strategies Using GPS Simulator And Spacecraft Attitude Control Simulator
… nonlinear attitude controllers with three reaction wheels as the control device. The angular rate controller successfully tracks a time varying attitude trajectory. The Modified Rodrigues Parmater (MRP) attitude controller results in successfully tracking the angular rates and MRP attitude …
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Theoretical and Experimental Investigation of Attitude Control for Underactuated Spacecraft
… actuatorsexternal thrusters, magnetorquers, and reaction wheelsare considered in the nonlinear rigid-body control problem. According to Brocketts theorem, a smooth or continuous feedback law does not exist in the attempt to stabilize the attitude dynamics, hence robust discontinuous control …
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Development and analysis of a small satellite attitude determination and control system testbed
… freedom, rotational air bearing, which uses four reaction wheels for attitude control and a series of sensors for attitude determination. The testbed includes all the equipment necessary to allow for closed loop testing of individual ADCS components and integrated ADCS systems in the simulated …
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Dynamic and thermal control of an electromagnetic formation flight testbed
… attitude using only electromagnetic forces and reaction wheels. A thorough description of this system is given, focusing on the development of its thermal and dynamic control. Innovations to the thermal system, used to cool the superconducting wire of the electromagnet, are described. All …
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Fast star tracker centroid algorithm for high performance CubeSat with air bearing validation
… control to achieve the pointing requirement. Reaction wheels provide coarse satellite attitude control while a high bandwidth piezoelectric stage performs fine optical stabilization. The optical sensor provides star images from which a centroiding algorithm estimates the star locations on the …
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Adaptive Control of VSCMGs for Satellite Attitude Tracking
… devices. Momentum management devices such as reaction wheels (RWs), control moment gyroscopes (CMGs), and variable speed control moment gyroscopes (VSCMGs) allow satellites to obtain high levels of pointing accuracy with minimal fuel expenditure. However, uncertainty in these devices can …
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Addressing Stability Robustness, Period Uncertainties, and Startup of Multiple-Period Repetitive Control for Spacecraft Jitter Mitigation
… of periodic excitation. Slight imbalance in reaction wheels used for attitude control creates three disturbance periods. A special RC structure was developed to allow one to address multiple unrelated periods which is referred to as Multiple-Period Repetitive Control (MPRC). MPRC in practice …
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Design and implementation of the state estimator for trajectory following of an electromagnetic formation flight testbed
… generated by superconducting magnets and the reaction torque generated by reaction wheels as the way to control position and attitude of each satellite respectively. Since all of the actuators in EMFF utilize solar energy and do not depend on consumables, the mission lifetime can be …
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Health Management and Adaptive Control of Distributed Spacecraft Systems
… attitude requirements that are achieved using Reaction Wheels as the control moment device. An adaptive control based on Deep Reinforcement Learning using an Actor-Critic-Adverse architecture is implemented to achieve high levels of mission protection, especially under disturbances that might …
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