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1
Giesselmann, Jens Uwe Michael, and jens giesselmann@gmx net. "Development of an Active Magnetic Attitude Determination and Control System for Picosatellites on highly inclined circular Low Earth Orbits." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070514.162516.
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Small satellites are becoming increasingly important to the aerospace industry mainly due to their significantly reduced development and launch cost as well as shorter development time frames. In order to meet the requirements imposed by critically limited resources of very small satellites, e.g. picosatellites, innovative approaches have to be taken in the design of effective subsystem technologies. This thesis presents the design of an active attitude determination and control system for flight testing on-board the picosatellite 'Compass-1' of the University of Applied Sciences Aachen, Germany. The spacecraft of the CubeSat class with a net spacecraft mass of only 1kg uses magnetic coils as the only means of actuation in order to satisfy operational requirements imposed by its imagery payload placed on a circular and polar Low Earth Orbit. The control system is capable of autonomously dissipating the tumbling rates of the spacecraft after launch interface separ ation and aligning the boresight of the payload into the desired nadir direction within a pointing error of approximately 10°. This nadir-pointing control is achieved by a full-state feedback Linear Quadratic Regulator which drives the attitude quaternion and their respective rates of change into the desired reference. The state of the spacecraft is determined by a static statistical QUEST attitude estimator processing readings of a three-axis magnetometer and a set of five sun sensors. Linear Floquet theory is applied to quantify the stability of the controller and a non-linear dynamics simulation is used to confirm that the attitude asymptotically converges to the reference in the absence of environmental disturbances. In the presence of disturbances the system under control suffers from fundamental underactuaction typical for purely magnetic attitude control but maintains satisfactory alignment accuracies within operational boundaries.
2
Bellini, Niccolo'. "Magnetic actuators for nanosatellite attitude control." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7506/.
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The research and the activities presented in the following thesis report have been led at the California Polytechnic State University (US) under the supervision of Prof. Jordi Puig Suari.
The objective of the research has been the study of magnetic actuators for nanosatellite attitude control, called magnetorquer. Theese actuators are generally divided in three different kinds: air core torquer, embedded coil and torquerod.
In a first phase of the activity, each technology has been analyzed, defining advantages and disadvantages, determining manufacturing procedures and creating mathematical model and designing equation. Dimensioning tools have been then implemented in numerical software to create an instrument that permits to determine the optimal configuration for defined requirements and constraints.
In a second phase of the activities the models created have been validated exploiting prototypes and proper instruments for measurements. The instruments and the material exploited for experiments and prototyping have been provided by the PolySat and CubeSat laboratories.
The results obtained led to the definition of a complete designing tool and procedure for nanosatellite magnetic actuators, introducing a cost analysis for each kind of solution.
The models and the tools have been maintained fully parametric in order to offer a universal re-scalable instrument for satellite of different dimension class.
3
Chen, Hung-Hsu Fred. "Ride and attitude control of active suspensions /." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487678444256792.
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Lundh, Joachim. "Model Predictive Control for Active Magnetic Bearings." Thesis, Linköpings universitet, Reglerteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-81325.
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This thesis discuss the possibility to position control a rotor levitated with active magnetic bearings. The controller type considered is model predictive control which is an online strategy that solves an optimization problem in every sample, making the model predictive controller computation-intense. Since the sampling time must be short to capture the dynamics of the rotor, very little time is left for the controller to perform the optimization. Different quadratic programming strategies are investigated to see if the problem can be solved in realtime. Additionally, the impact of the choices of prediction horizon, control horizon and terminal cost is discussed. Simulations showing the characteristics of these choises are made and the result is shown.<br>Det här examensarbetet diskuterar möjligheten att positionsreglera en rotor som leviteras på aktiva magnetlager. Reglerstrategin som används är modellbaserad prediktionsreglering vilket är en online-metod där ett optimeringsproblem löses i varje sampel. Detta gör att regulatorn blir mycket beräkningskrävande. Samplingstiden för systemet är mycket kort för att fånga dynamiken hos rotorn. Det betyder att regulatorn inte ges mycket tid att lösa optimeringsproblemet. Olika metoder för att lösa QP-problem betraktas för att se om det är möjligt att köra regulatorn i realtid. Dessutom diskuteras hur valet av prediktionshorisont, reglerhorisont och straff på sluttillståndet påverkar regleringen. Simuleringar som visar karakteristiken av dessa val har utförts.
5
You, Silu. "Adaptive Backstepping Control of Active Magnetic Bearings." Cleveland State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=csu1273679767.
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6
Li, Peichao. "Active touchdown bearing control in magnetic bearing systems." Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678846.
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7
Khader, Shahbaz Abdul. "System Identification of Active Magnetic Bearing for Commissioning." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-243630.
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Active magnetic bearing (AMB) is an ideal bearing solution for high performance and energy efficient applications. Proper operation of AMB can be achieved only with advanced feedback control techniques. An identified system model is required for synthesizing high performance model based controllers. System identification is the preferred method for obtaining an accurate model. Therefore, it becomes a prerequisite for the commissioning of AMB. System identification for commissioning poses some challenges and special requirements. In this thesis, system identification of AMB is approached within the context of commissioning. A procedure for identification is developed and applied to experimental data from a prototype AMB system. The identification procedure is based on the so called prediction error method, and it has been performed in the frequency domain. A linear state-space model, along with the required parameters, is successfully identified.
8
Pappagallo, Isabella. "Numerical investigation of magnetic only attitude control for small satellites." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18306/.
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The subject of the thesis research is the study of the attitude control for small satellites actuated by only magnetorquers, which presents interesting control challenges due to the time-variance and underactuation of the system. It is indeed known that for underactuated systems, the presence of external disturbances can lead to system instability. Even if the problem of finding a robust non-linear global controller has been already investigated, there is still room for improvements.
In this regard, the present work proposes a solution in which the elements of the averaging theory for a system subjected to exogenous input can be combined with that of the sliding mode control theory based on a classical optimal sliding manifold, providing the feedback system with robustness against disturbances. The proposed approach is applied to design an Earth-pointing attitude control system for the ESEO spacecraft in Low Earth Orbit.
The results of simulations suggest that the sliding mode control as robust control feedback provides good performances in the presence of external disturbances, measurement noises, and inertia uncertainties.
9
Lehner, Maximilian Jacob. "Study and design of magnetic attitude control systems for nanosatellites." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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The objective of this bachelor thesis was to display all the attitude and control systems (ACS) available for CubeSats and how magnetic ACS are the most convenient option in terms of volume. Precisely this project focused on the procedure, the design and the laws of physics that are behind the creation of a torque rod, a magnetic attitude and control system conceived for nanosatellites.
After discussing the magnetic laws, the different types of materials of the core, and the geometric parameters of the core and of the wire, all of which determine the operating area of the system, a theoretical model for a torque rod was devised.
This was done by using the models present in Niccolò Bellini’s master thesis “Magnetic actuators for nanosatellite attitude control”, 2014.
This bachelor thesis ended with the gathering of some experimental data on an embedded magnetorquer collected through a Helmholtz cage.
10
Zhou, F. B. "Transputer-based digital control of an active magnetic bearing system." Thesis, University of Salford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360386.
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Baldi, Pietro <1981>. "Fault detection, diagnosis and active fault tolerant control for a satellite attitude control system." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/6983/.
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Modern control systems are becoming more and more complex and control algorithms more and more sophisticated. Consequently, Fault Detection and Diagnosis (FDD) and Fault Tolerant Control (FTC) have gained central importance over the past decades, due to the increasing requirements of availability, cost efficiency, reliability and operating safety.
This thesis deals with the FDD and FTC problems in a spacecraft Attitude Determination and Control System (ADCS). Firstly, the detailed nonlinear models of the spacecraft attitude dynamics and kinematics are described, along with the dynamic models of the actuators and main external disturbance sources. The considered ADCS is composed of an array of four redundant reaction wheels. A set of sensors provides satellite angular velocity, attitude and flywheel spin rate information. Then, general overviews of the Fault Detection and Isolation (FDI), Fault Estimation (FE) and Fault Tolerant Control (FTC) problems are presented, and the design and implementation of a novel diagnosis system is described. The system consists of a FDI module composed of properly organized model-based residual filters, exploiting the available input and output information for the detection and localization of an occurred fault. A proper fault mapping procedure and the nonlinear geometric approach are exploited to design residual filters explicitly decoupled from the external aerodynamic disturbance and sensitive to specific sets of faults. The subsequent use of suitable adaptive FE algorithms, based on the exploitation of radial basis function neural networks, allows to obtain accurate fault estimations.
Finally, this estimation is actively exploited in a FTC scheme to achieve a suitable fault accommodation and guarantee the desired control performances. A standard sliding mode controller is implemented for attitude stabilization and control. Several simulation results are given to highlight the performances of the overall designed system in case of different types of faults affecting the ADCS actuators and sensors.
12
Choi, Heeju. "Intelligent Control Using Confidence Interval Networks: Applications to Robust Control of Active Magnetic Bearings." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-04062005-113722/.
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Robust control synthesis requires an explicit mathematical description of the system dynamics (a model) and uncertainty bounds associated with that model. These uncertainty bounds are usually chosen arbitrarily and conservatively for guaranteed stability, frequently at the expense of controller performance. This research demonstrates the application of Confidence Interval Networks (CINs), unique artificial neural networks that utilize asymmetric bilinear error cost functions, for estimating the bounds of model uncertainty required for robust control synthesis. A highly nonlinear and unstable active magnetic bearing (AMB) system is considered. A high-speed flexible rotor supported by AMBs is modeled using analytical approaches, finite element analysis, and system identification. CINs learn the statistical bounds of model uncertainty resulting from unmodeled dynamics and parameter variations. These bounds are incorporated into the synthesis of multivariable robust controllers based on two approaches, linear time invariant and linear parameter varying. Experimental results on a multivariable AMB test rig reveal the benefits of this combination of intelligent system identification and robust control: significant performance improvements vs. conventional robust control with and without mass imbalance (process disturbances).
13
Jayanth, Vignesh. "Identification and Control of Flexible Structures Supported on Active Magnetic Bearings." NCSU, 2001. http://www.lib.ncsu.edu/theses/available/etd-20010926-183814.
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<p>The focus of this thesis is the development and demonstration of adaptive control algorithms for Active Magnetic Bearings AMBs) that account for uncertainties associated with structural vibration modes. A flexible rotor AMB test rig is designed and modeled using Finite Element Analysis (FEA). The flexible modes and equations of motion are obtained using modal analysis techniques. Typically, such analyses accurately predict the low frequency modes, but accuracy at higher frequencies is greatly reduced. Adaptive control algorithms that account for parametric uncertainties and unmodeled dynamics are developed to levitate and control the flexible rotor. Model parameters for the system are identified using recursive least squares, and used to update a self-tuning pole-placement controller. This self-tuning approach dramatically improves the performance and robustness of the magnetic levitation system, as demonstrated through simulations and experimental demonstrations. The flexible rotor AMB test rig is fabricated to experimentally validate the identification and control algorithms. Results clearly demonstrate the performance and limitations of the adaptive control design.<P>
14
Wilson, Brian Christopher David. "Control Designs for Low-Loss Active Magnetic Bearing: Theory and Implementation." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-04122004-133631/unrestricted/wilson%5Fbrian%5Fc%5F200405%5Fphd.pdf.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2004.<br>Habetler, Thomas, Committee Member ; Sadegh Nader, Committee Member ; Taylor David, Committee Member ; Tsiotras Panagiotis, Committee Co-Chair ; Heck-Ferri Bonnie, Committee Co-Chair. Vita. Includes bibliographical references (leaves 319-326).
15
Aragón, Ayala Danielo Eduardo. "Optimal control for a prototype of an active magnetic bearing system." Master's thesis, Pontificia Universidad Católica del Perú, 2017. http://tesis.pucp.edu.pe/repositorio/handle/123456789/8675.
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First applications of the electromagnetic suspension principle have been in experimental
physics, and suggestions to use this principle for suspending transportation
vehicles for high-speed trains go back to 1937. There are various ways of designing
magnetic suspensions for a contact free support, the magnetic bearing is just one of
them [BCK+09].
Most bearings are used in applications involving rotation. Nowadays, the use of
contact bearings solves problems in the consumer products, industrial machinery, or
transportation equipment (cars, trucks, bicycles, etc). Bearings allow the transmition
of power from a motor to moving parts of a rotating machine [M+92].
For a variety of rotating machines, it would be advantageous to replace the mechanical
bearings for magnetic bearings, which rely on magnetic elds to perform
the same functions of levitation, centering, and thrust control of the rotating parts
as those performed by a mechanical bearing. An advantage of the magnetic bearings
(controlled or not) against purely mechanical is that magnetic bearings are contactless
[BHP12]. As a consequence these properties allow novel constructions, high
speeds with the possibility of active vibration control, operation with no mechanical
wear, less maintenance and therefore lower costs. On the other hand, the complexity
of the active (controlled) and passive (not controlled) magnetic bearings requires
more knowledge from mechanics, electronics and control [LJKA06].
The passive magnetic bearing (PMB) presents low power loss because of the
absence of current, lack of active control ability and low damping sti ness [FM01,
SH08]. On the other hand, active magnetic bearing (AMB) has better control ability
and high sti ness, whereas it su ers from high power loss due to the biased current
[JJYX09].
Scientists of the 1930s began investigating active systems using electromagnets for high-speed ultracentrifuges. However, not controlled magnetic bearings are physically
unstable and controlled systems only provide proper sti ness and damping
through sophisticated controllers and algorithms. This is precisely why, until the
last decade, magnetic bearings did not become a practical alternative to rolling element
bearings. Today, magnetic bearing technology has become viable because of
advances in microprocessing controllers that allow for con dent and robust active
control [CJM04].
Magnetic bearings operate contactlessly and are therefore free of lubricant and
wear. They are largely immune to heat, cold and aggressive substances and are operational
in vacuum. Because of their low energy losses they are suited for applications
with high rotation speeds. The forces act through an air gap, which allows magnetic
suspension through hermetic encapsulations [Bet00].<br>Tesis
16
Rudd, Brent. "Active Tonal and Broadband Noise Control for Magnetic Resonance Imaging Systems." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1298042881.
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Walker, Alex R. "Fuzzy Attitude Control of a Magnetically Actuated CubeSat." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1384333499.
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Herbert, Eric W. "NPSAT1 magnetic attitude control system algorithm verification, validation, and air-bearing tests." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Sep%5FHerbert.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, Sept. 2004.<br>Thesis advisor(s): Barry Leonard, Xiaoping Yun. Includes bibliographical references (p. 185-186). Also available online.
19
Tombul, Galip Serdar. "On the application of nonlinear systems theory to active magnetic bearings." Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578704.
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Gibson, Nathan Scott. "H-infinity Control of Active Magnetic Bearings: An Intelligent Uncertainty Modeling Approach." NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-11302004-135840/.
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Robust control techniques require a dynamic model of the plant and bounds on model uncertainty to formulate control laws with guaranteed stability. Although techniques for modeling and identifying dynamic systems are well established, very few procedures exist for estimating uncertainty bounds. In the case of H-infinity control synthesis, a conservative weighting function for model uncertainty is usually chosen to ensure closed-loop stability over the entire operating space. The primary drawback of this conservative, "hard computing" approach is reduced performance due to the number of plants the resulting controller can stabilize. This paper demonstrates a novel "soft computing" approach to estimate bounds of model uncertainty resulting from parameter variations, unmodeled dynamics, and non-deterministic processes in dynamic plants. This approach uses confidence interval networks (CINs), radial basis function neural networks trained using asymmetric bilinear error cost functions, to estimate confidence intervals on the uncertainty associated with nominal linear models for robust control synthesis. This research couples the hard computing features of H-infinity control with the soft computing characteristics of intelligent system identification, and realizes the combined advantages of both. Experimental demonstrations conducted on a multivariable, flexible-rotor active magnetic bearing system confirm these capabilities.
21
Marais, Charl Henri. "High speed flexible rotor active magnetic bearing control / by Charl Henri Marais." Thesis, North-West University, 2006. http://hdl.handle.net/10394/1084.
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The School of Electrical, Electronic and Computer Engineering at the North-West University is in the
process of establishing a knowledge base on Active Magnetic Bearings (AMBs). In support of this
initiative this project is aimed at characterising an in-house developed double radial heteropolar AMB
system.
Before characterising the AMB system the acoustic noise problem of the system had to be addressed and
reduced to an acceptable level. To reduce the acoustic noise of the system a noise analysis was done to
determine the source of the noise. The analysis revealed radiated noise from the electromagnets and
power amplifiers (PA) and conducted noise on the signals to and from the controller. The conducted noise
is reduced by using anti-aliasing (AAF) and anti-imaging filters (AIF) before and after the controller. The
effect of the radiated noise is reduced by synchronising the sampling of the sensor signals with the
switching of the PAS.
The characterisation of the AMB system starts with a Mass-Spring-Damper (MSD) simulation which is
a linear representation of the AMB system. This simulation is used to understand the basic principles of a
second order system and to compare its response to the nonlinear AMB simulation. The following step in
characterising the AMB system is to determine the effect of filters on the nonlinear AMB simulation and
to determine the simulation characteristics. These characteristics are compared to the MSD simulation
and the actual AMB system. The characteristics compared between the MSD and AMB simulations are
the static, second order and dynamic stiffness.
The actual AMB system was characterised before and after the AAF and AIF were implemented. This
provided the opportunity to determine the effects of the filters on the actual system and not just from
simulations. The characteristics measured on the actual AMB system include the static stiffness, dynamic
stiffness, rotor dynamics and system sensitivity. The stiffness characteristics of the actual AMB system
showed good correlation with the linear and nonlinear simulations. The measured results showed a
decrease in static stiffness and an increase in system sensitivity because of the AAF, AIF and controller
pole. It also showed that the effects of the filters can be reduced by moving the controller pole to a higher
frequency.
The characterisation of the double radial heteropolar AMB system provides a fundamental understanding
of the AMB performance aiding the AMB design process.<br>Thesis (M. Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2006.
22
Lozano, Jauregui John Hugo. "Control for an active magnetic bearing machine with two hybrid electromagnet actuators." Master's thesis, Pontificia Universidad Católica del Perú, 2021. http://hdl.handle.net/20.500.12404/19548.
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This thesis work begins with the revision of state of the art about active magnetic bearings
(AMB), the mathematical methods used to obtain geometric and physical parameters that
will influence in the mechanical, electrical design and control system proposed by this
prototype.
The control system will activate the magnetic bearing to center its shaft, for which it is joined
a variable load in order to study the best control performance under different load over the
rotor proposed by requirements. When the rotor is not controlled in its own axis even though
variable load, a position error will occur that will be corrected by the program of a control
system that will center the shaft (rotor).
For this design was evaluated generalized AMB models [2], [3], [4] to validate the best
identification for this design, furthermore as a consequence to get the best performance for
the control system as it was achieved by generalized models and it was evaluated the
advantage of this AMB machine through “Two hybrid electromagnet actuators” and variable
load fixed to its shaft. For this reason, it was necessary to test a simple AMB with only one
electromagnet actuator [4], due to compare enhancement of hybrid characteristics for the
electromagnet actuators, for which, also it was evaluated how many actuators could be
necessary to join to an AMB system with the target to get the control. It means, in this work
there are comparisons between a simple AMB, generalized AMB models and this design,
owing to show the achievements of this design.
In order to show experimental results in state of the art, it is known that Siemens presented
Simotics Active Magnetic Bearings technology for wear free operation in large – machine
applications, regulated magnetic fields hold the rotor in suspension precisely without oil or
contact, to make this task, sensors capture the position of the shaft 16000 times per second
and a regulator adjusts the magnetic field to keep the rotor hovering precisely in the bearing
center [1].
By other side the author [4] describes the experimental results in which is proposed that at
low speed the bearing parameters are mainly determined by the controller characteristics.
While at high speed, the bearing parameters are not only related to the control rule but also
related to the speed. This may be due to the influence of eddying effect. [4]
Furthermore, by author [3], the algorithm to get fast responses in front of disturbances, the
disadvantages of these algorithms are given by not enough memory space to execute them,
due to computing time is short compared with rotor displacement response time, and it is
defined that it could be possible to execute the control algorithm through a real-time
operating system to obtain the desired response [3].
Finally, in reference [6] it is described about filtering every noise as additive white
Gaussian noise, by a predictive filter, which is obtained by analyzing Least Mean Square
(LMS) and feedback/feedforward algorithm.
23
Jiménez, Samuel. "Internal sensing and actuation topologies for active rotors." Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.715252.
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Active control constitutes the state of the art in vibration management in rotating machines. However, existing designs are impractical and costly, and hence not yet widely applied. The goal of the research reported here was to develop a design which would allow the implementation of active technology in a wider range of rotating machine applications. Thus, this study focuses on a novel active rotor topology, consisting of a hollow rotor with internally mounted sensors and actuators. This layout provides greater freedom to select the sensor and actuator positions along the rotor, and naturally protects the devices from harsh working environments. The research was structured according to four themes. Firstly, the concept feasibility was explored by constructing a fully functioning prototype. MEMS accelerometers and mass balancer actuators were mounted in an assembled rotor, together with a microcontroller and radio unit to enable wireless transmission of data. Secondly, the behaviour of MEMS accelerometers in a rotating frame of reference was studied. An output model was derived and applied to the study of whirl orbits and transient vibration. Further, techniques were developed to extract mean displacement and angular velocity information from the sensor signals. An analysis of potential sources of measurement error was conducted, and methods for their mitigation devised. The third theme focused on developing active vibration control techniques suitable for use with active rotors. The core of this work is the development and successful implementation of a non a priori method, Algorithmic Direct Search Control. This technique enables vibration to be minimised without knowledge of the system characteristics, by applying a direct search optimisation technique as a control law. Finally, the combination of active rotors and Active Magnetic Bearings was considered to tackle the problem of sensor/actuator non-collocation. The challenge of levitating a rotor on AMBs using only internal accelerometers was approached via integration-based displacement information extraction, to exploit existing PID controllers. This method proved unfeasible in practice, but valuable lessons were derived from the study. The key finding of this work is that active rotor technology is versatile, cost-effective, powerful and feasible. As such, it offers great potential as a route to achieving a more practical and generalised implementation of active control technology in rotating machinery.
24
Mendoza, Hector. "Evaluation of the Effectiveness of an Active Magnetic Damper (AMD) in Damping Subsynchronous Vibrations in a Flexible Rotor." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/33887.
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Subsynchronous vibrations such as those caused by rotor instability represent one of the most harrowing scenarios of rotor vibration. They are related to a great diversity of destabilizing forces and some of them are not well understood yet. Therefore, special attention must be paid to this type of vibration. Active Magnetic Bearings (AMBs) monitor the position of the shaft and change the dynamics of the system accordingly to keep the rotor in a desired position, offering the possibility of being used as dampers for vibration control.
In the present work, a single-disk and a three-disk rotor were built to evaluate the effectiveness of an Active Magnetic Damper (AMD) in damping subsynchronous vibrations. An AMD was used to inject a signal simulating a subsynchronous vibration in the rotor, as another AMD was used to perform active control. Two locations of the AMD were considered for each rotor. For the single-disk rotor, experimental data was taken with the AMD located at three-quarters of the rotor-span and with the AMD located at midspan. For the three-disk rotor, experimental data was taken with the AMD located at a quarter-span and with the AMD at two-thirds of the rotor span.
An undamped critical speed and a forced response analysis were performed on the rotors in order to predict the dynamic characteristics of the rotors with and without the AMD.
It was demonstrated that an AMD is effective in damping subsynchronous vibrations. The addition of an AMD introduces damping and stiffness to the rotor-bearing system resulting in a change in the synchronous response and a consequent increase of the amplitude of vibrations at synchronous frequencies. This effect must be carefully considered when designing a system with an AMD.<br>Master of Science
25
Stott, John Dougal Zebedee. "A comparative study on the control of active magnetic bearings / by J.D.Z. Stott." Thesis, North-West University, 2005. http://hdl.handle.net/10394/959.
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The aim of this project is to perform a comparative study on different control techniques applied
to active magnetic bearings (AMBs). The project will involve the evaluation of two suitable
nonlinear modem control techniques on an existing model to illustrate their superior
performance over conventional linear control techniques. The techniques under investigation are
classical PD control, fuzzy logic control and sliding mode control.
As a first step the experimental model was characterised and found to be inadequate for a
meaningful comparative control study. The physical model was improved in terms of sensor
linearization, power amplifier configuration and magnetic circuit layout. A comprehensive
matched simulation model of the experimental model is then developed to serve as the design
platform for the mentioned controllers.
The comparative study commences with the optimisation of a classical PD controller for the
experimental model. This controller is used as benchmark for performance comparison. An
equivalent linear fuzzy logic controller is then derived from the PD controller. Finally a control
law is derived for a sliding mode controller.
The performances of the different controllers are evaluated for step inputs of 1000, 200 and
1500 pm respectively. The simulated PD and fuzzy logic responses showed remarkable
correlation as well as the experimental results. The sliding mode controller is simulated and
intuitively optimised. The simulated and practical responses of the sliding mode controller also
showed good correlation. Some differences in the response are attributed to implementation
discrepancies.
The controllers are compared in terms of the equivalent stiffness and damping of the different
systems. The ITAE performance index is used as an additional comparative criterion and
identified the sliding mode controller as superior to the linear controllers.
This project emphasises the importance of accurate modelling. Future work will involve
delinearization of the fuzzy logic controller and a specialised study on sliding mode control.<br>Thesis (M.Ing. (Electrical and Electronic Engineering))--North-West University, Potchefstroom Campus, 2006.
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Herbst, Dewald. "Single board computer based control of an active magnetic bearing / by Dewald Herbst." Thesis, North-West University, 2008. http://hdl.handle.net/10394/2641.
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The McTronX Research group at the North-West University is currently conducting research in the use of active magnetic bearings (AMBs) for a flywheel energy storage system (FESS). Together with this, the aim of this project is to take the level of control of such AMB systems to an industrial level. Instead of using a rapid prototype dSPACE® controller, a single board computer (SBC) is proposed. Issues to be addressed, includes: SBC overview, control system specifications, skills development for SBC, implementation and evaluation.
All the digital and analogue input/output signal requirements for the FESS are determined prior to specifying an SBC. Six different SBCs were compared and in the end the SBC6713ell from Innovative Integration (II) was chosen and sourced. The SBC6713ell complies with all the requirements specified by the client.
Two interface boards were used to integrate the SBC with the FESS. The first board contained all the protection circuitry to protect the controller from faults that could occur on the sensor and actuator side of the FESS and is used to connect the dSPACE® to the FESS without the SBC. After the hardware was integrated, the software/firmware integration started. On the SBC, the PD control was implemented for the AMBs as well as the voltage over frequency control for the PMSM. A graphical user interface (GUI) was further developed on a host computer to monitor the FESS.
Four tests were done on the integration of the SBC with the FESS. Firstly the performance of the controller with regard to the control algorithms was tested. The stability and sensitivity analyses of the system followed and ended with the PMSM start-up test. The control algorithm execution time was longer than expected and adjustments to the sampling time had to be made. Stability tests showed a decrease in bearing stiffness and damping, which was due to low pass filters on the analogue to digital converter board. The sensitivity of the system also increased due to the effect of the filters on the system.
The inconsistency in bearing damping and stiffness, obtained from the stability tests was verified by adding the filters to the simulation. These filters caused an attenuation of less than 1 dB, but resulted in a phase shift of -36.3° in the control loop.
Industrial control was realised using an SBC, but further work is still necessary. The areas identified for future work is: non linear control algorithms, low noise digital power amplifiers, speed sensor and the PMSM drive.<br>Thesis (M.Ing. (Electrical and Electronic Engineering))--North-West University, Potchefstroom Campus, 2008.
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Mykhaylyshyn, Volodymyr. "Application of Active Magnetic Force Actuator for Control of Flexible Rotor System Vibrations." Cleveland State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=csu1322845232.
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Moorthy, Ananthalakshmy Krishna. "EXTENDED ORBITAL FLIGHT OF A CUBESAT IN THE LOWER THERMOSPHERE WITH ACTIVE ATTITUDE CONTROL." Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-dissertations/558.
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A wide variety of scientifically interesting missions could be enabled by orbital flight altitudes of 150 – 250 km. For the present work, this range of altitudes is defined as extremely Low Earth Orbit (eLEO). The use of low-cost nanosatellites (mass < 10 kg) has reduced the cost barrier to orbital flight over the last decade and the present study investigates the feasibility of using primarily commercial, off-the-shelf (COTS) hardware to build a nanosat specifically to allow extended mission times in eLEO. CubeSats flying in the lower thermosphere have the potential to enable close monitoring of the Earth’s surface for scientific, commercial, and defense-related missions. The results of this research show that the proper selection of primary and attitude control thrusters combined with precise control techniques result in significant extension of the orbital life of a CubeSat in eLEO, thus allowing detailed explorations of the atmosphere. In this study, the orbit maintenance controller is designed to maintain a mission-averaged, mean altitude of 244 km. An estimate is made of the primary disturbance torque due to aerodynamic drag using a high-fidelity calculation of the rarefied gas drag based on a Direct Simulation, Monte-Carlo simulation. The primary propulsion system consists of a pair of electrospray thrusters providing a combined thrust of 0.12 mN at 1 W. Results of a trade study to select the best attitude control option indicate pulsed plasma thrusters operating at 1 W are preferable to reaction wheels or mangetorquers at the selected altitude. An extended Kalman filter is used for orbital position and spacecraft attitude estimations. The attitude determination system consists of sun sensors, magnetometers, gyroscopes serving as attitude sensors. The mission consists of two phases. In Phase I, a 4U CubeSat is deployed from a 414 km orbit and uses the primary propulsion system to deorbit to an initial altitude within the targeted range of 244 +/- 10 km. Phase I lasts 12.73 days with the propulsion system consuming 5.6 g of propellant to deliver a ∆V of 28.12 m/s. In Phase II the mission is maintained until the remaining 25.2 g of propellant is consumed. Phase II lasts for 30.27 days, corresponding to a ∆V of 57.22 m/s with a mean altitude of 244 km. The mean altitude for an individual orbit over the entire mission was found to vary from a maximum of 252 km to a minimum of 236 km. Using this approach, a primary mission life of 30.27 days could be achieved, compared with 3.1 days without primary propulsion.
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Zirkle, Todd A. "Analysis of a magnetic three-axis stabilized attitude control system for the NPSAT1 spacecraft." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA397962.
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Thesis (M.S. in Space Systems Operations) Naval Postgraduate School, September 2001.<br>Thesis advisor(s): Spencer, Michael. "September 2001". Includes bibliographical references (p. 91). Also available online.
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Combrinck, Angelique. "Adaptive control of an active magnetic bearing flywheel system using neural networks / Angelique Combrinck." Thesis, North-West University, 2010. http://hdl.handle.net/10394/4457.
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The School of Electrical, Electronic and Computer Engineering at the North-West University in
Potchefstroom has established an active magnetic bearing (AMB) research group called McTronX.
This group provides extensive knowledge and experience in the theory and application of AMBs. By
making use of the expertise contained within McTronX and the rest of the control engineering
community, an adaptive controller for an AMB flywheel system is implemented.
The adaptive controller is faced with many challenges because AMB systems are multivariable,
nonlinear, dynamic and inherently unstable systems. It is no wonder that existing AMB models are
poor approximations of reality. This modelling problem is avoided because the adaptive controller is
based on an indirect adaptive control law. Online system identification is performed by a neural
network to obtain a better model of the AMB flywheel system. More specifically, a nonlinear autoregressive
with exogenous inputs (NARX) neural network is implemented as an online observer.
Changes in the AMB flywheel system’s environment also add uncertainty to the control problem. The
adaptive controller adjusts to these changes as opposed to a robust controller which operates despite
the changes. Making use of reinforcement learning because no online training data can be obtained, an
adaptive critic model is applied. The adaptive controller consists of three neural networks: a critic, an
actor and an observer. It is called an observer-based adaptive critic neural controller (ACNC).
Genetic algorithms are used as global optimization tools to obtain values for the parameters of the
observer, critic and actor. These parameters include the number of neurons and the learning rate for
each neural network. Since the observer uses a different error signal than the actor and critic, its
parameters are optimized separately. When the actor and critic parameters are optimized by
minimizing the tracking error, the observer parameters are kept constant.
The chosen adaptive control design boasts analytical proofs of stability using Lyapunov stability
analysis methods. These proofs clearly confirm that the design ensures stable simultaneous
identification and tracking of the AMB flywheel system. Performance verification is achieved by step
response, robustness and stability analysis. The final adaptive control system remains stable in the
presence of severe cross-coupling effects whereas the original decentralized PD control system
destabilizes. This study provides the justification for further research into adaptive control using
artificial intelligence techniques as applied to the AMB flywheel system.<br>Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2011.
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Steyn, Stephanus Jacobus Marais. "Multivariable H control for an active magnetic bearing flywheel system / Stephanus Jacobus Marais Steyn." Thesis, North-West University, 2010. http://hdl.handle.net/10394/4939.
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Objectives: The aims of this pilot study were to quantify respiratory and potential dermal exposure of nail
technicians to acetone, formaldehyde, ethyl methacrylate, methyl methacrylate, toluene and xylene. Fifteen female
nail technicians, working in different salons participated in this study. Products used for nail treatments differed
between salons. Most salons used acrylate based nail products whereas others used UV–gel products exclusively.
Methods: The participants were divided into two groups, those who used acrylate– and those who used UV–gel
products exclusively. Eight hour personal respiration exposure to acetone, formaldehyde, ethyl methacrylate,
methyl methacrylate, toluene and xylene were determined. The concentration of airborne volatile organic
compounds in the salons was also determined with the use of a direct reading instrument (EntryRAE). Potential
dermal exposure to the above mentioned solvents (excluding formaldehyde) was determined with the use of
charcoal pads (surrogate skin method). During respiratory and dermal sampling, observations were made regarding
work practices and control measures used in the salons. Results: It was found that the eight hour time weighed
average exposure is well below the recommended occupational exposure limits of the individual chemicals and
showed no additive effect. The highest mean respiratory exposures in both groups were acetone (27.22 mg/m3 and
28.36 mg/m3). EntryRAE results showed peak periods of exposure to volatile organic compounds during the day
(322.16 ppm) that were much higher than the average eight hour exposure (0.21 ppm). The two groups’ exposure
levels were compared to determine if there is a significant difference between the exposures levels but no
statistically significant difference was found. The dermal exposures on hand and neck to acetone, ethyl
methacrylate and methyl methacrylate showed strong significant correlations to the concordant chemical’s
respiratory exposures. Correlations between air and dermal exposure was calculated once more after adjusting
dermal exposure but the findings indicated only one statistically significant correlation of 0.42 in the case of ethyl
methacrylate. Conclusion: Nail technicians are not at immediate health risk as the exposure in nail salons are well
below recommended occupational exposure limits. However the unknown effects of chronic low level exposure to
solvents and the large number of previous studies that reported increased health risks in nail technicians must also
be considered. The use of methyl methacrylate in nail products sold in South Africa is also worrying as methyl
methacrylate is banned by the FDA in the US due to its skin sensitisation potential that may lead to allergic contact
dermatitis. The methods used to determine potential dermal exposure as well as adjusted dermal exposure remains
problematic. This is due to the high percentage of adjusted dermal exposure values that had to be estimated and the
fact that the activated charcoal pads have a higher absorption potential than human skin. Both methods must be
improved to increase accuracy of results. Observations and EntryRAE results demonstrated the irregular nature of
a nail technician’s work shift as well tasks performed from day to day. This complicates gathering data that is
representative of a nail technicians eight hour exposure. Therefore to further improve accuracy of results, sampling
should in future be task specific. Conventional ball–bearings in rotational applications can potentially be replaced by active magnetic bearings (AMBs). AMBs levitate the rotor via contact–free, actively controlled, electromagnetic forces. At the North–West University, AMBs are applied to a flywheel unin–terrupted power supply (Fly–UPS) system. Regrettably, AMBs are inherently open–loop un–stable because of the inverse displacement–force relationship, and for this reason requires closed–loop feedback control. Thus, the feasibility of multivariable H control for a Fly–UPS system is investigated. At present, the Fly–UPS system is being controlled by a number of decentralized single–input single–output (SISO), PD controllers. Ultimately, the combination of a multivariable plant, inherent instability, model uncertainties, cross–coupled stiffness, high rotational speed as well as external disturbances, calls for the development of a multivariable robust H controller. The aim of H control is to compute a controller such that the modelling uncertainties, noise and disturbances are minimized according to predefined performance and robustness re–quirements. A state–space model of both the radial AMBs and the axial AMB of the Fly–UPS system is developed and modelled according to the parameters of the physical rotor system. The sen–sors, power amplifiers and anti–aliasing filters are modelled and cascaded onto the rotor model. Finally, the system response is evaluated whereby the developed multivariable model is verified and validated. In the context of robust H control, it is vital in specifying the uncertainty bound (difference weighting function) between the mathematical model and physical system in order to ascer–tain stability robustness. Thus, the additive uncertainties between the nominal simulation model and the physical model at varied rotational speeds are characterised. Furthermore, the mixed sensitivity H control synthesis strategy is described. Different weighting schemes are explained and the six block problem weighting scheme is used for H controller synthesis. A multivariable controller is synthesised with weighting functions relevant to the AMB Fly–UPS system and the controller is reduced to a 19th order controller for implementation.<br>Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2011.
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Cade, Iain Stuart. "A wavelet based approach to the transient control of rotor/active magnetic bearing systems." Thesis, University of Bath, 2006. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426295.
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Kandil, Mohamed Salah. "Sliding mode control of active magnetic bearings with low losses : a model-free approach." Thèse, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/10166.
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Abstract : Over the past three decades, various fields have witnessed a successful application of active magnetic bearing (AMB) systems. Their favorable features include supporting high-speed rotation, low power consumption, and rotor dynamics control. Although their losses are much lower than roller bearings, these losses could limit the operation in some applications such as flywheel energy storage systems and vacuum applications. Many researchers focused their efforts on boosting magnetic bearings energy efficiency via minimizing currents supplied to electromagnetic coils either by a software solution or a hardware solution. According to a previous study, we adopt the hardware solution in this thesis. More specifically, we investigate developing an efficient and yet simple control scheme for regulating a permanent magnet-biased active magnetic bearing system. The control objective here is to suppress the rotor vibrations and reduce the corresponding control currents as possible throughout a wide operating range. Although adopting the hardware approach could achieve an energy-efficient AMB, employing an advanced control scheme could achieve a further reduction in power consumption. Many advanced control techniques have been proposed in the literature to achieve a satisfactory performance. However, the complexity of the majority of control schemes and the potential requirement of powerful platform could discourage their application in practice. The motivation behind this work is to improve the closed-loop performance without the need to do model identification and following the conventional procedure for developing a model-based controller. Here, we propose applying the hybridization concept to exploit the classical PID control and some nonlinear control tools such as first- and second-order sliding mode control, high gain observer, backstepping, and adaptive techniques to develop efficient and practical control schemes. All developed control schemes in this thesis are digitally implemented and validated on the eZdsp F2812 control board. Therefore, the applicability of the proposed model-free techniques for practical application is demonstrated. Furthermore, some of the proposed control schemes successfully achieve a good compromise between the objectives of rotor vibration attenuation and control currents minimization over a wide operating range.<br>Résumé: Au cours des trois dernières décennies, divers domaines ont connu une application réussie des systèmes de paliers magnétiques actifs (PMA). Leurs caractéristiques favorables comprennent une capacité de rotation à grande vitesse, une faible consommation d'énergie, et le contrôle de la dynamique du rotor. Bien que leurs pertes soient beaucoup plus basses que les roulements à rouleaux, ces pertes pourraient limiter l'opération dans certaines applications telles que les systèmes de stockage d'énergie à volant d'inertie et les applications sous vide. De nombreux chercheurs ont concentré leurs efforts sur le renforcement de l'efficacité énergétique des paliers magnétiques par la minimisation des courants fournis aux bobines électromagnétiques soit par une solution logicielle, soit par une solution matérielle. Selon une étude précédente, nous adoptons la solution matérielle dans cette thèse. Plus précisément, nous étudions le développement d'un système de contrôle efficace et simple pour réguler un système de palier magnétique actif à aimant permanent polarisé. L'objectif de contrôle ici est de supprimer les vibrations du rotor et de réduire les courants de commande correspondants autant que possible tout au long d'une large plage de fonctionnement. Bien que l'adoption de l'approche matérielle pourrait atteindre un PMA économe en énergie, un système de contrôle avancé pourrait parvenir à une réduction supplémentaire de la consommation d'énergie. De nombreuses techniques de contrôle avancées ont été proposées dans la littérature pour obtenir une performance satisfaisante. Cependant, la complexité de la majorité des systèmes de contrôle et l'exigence potentielle d’une plate-forme puissante pourrait décourager leur application dans la pratique. La motivation derrière ce travail est d'améliorer les performances en boucle fermée, sans la nécessité de procéder à l'identification du modèle et en suivant la procédure classique pour développer un contrôleur basé sur un modèle. Ici, nous proposons l'application du concept d'hybridation pour exploiter le contrôle PID classique et certains outils de contrôle non linéaires tels que contrôle par mode glissement du premier et du second ordre, observateur à grand gain, backstepping et techniques adaptatives pour développer des systèmes de contrôle efficaces et pratiques. Tous les systèmes de contrôle développés dans cette thèse sont numériquement mis en oeuvre et évaluées sur la carte de contrôle eZdsp F2812. Par conséquent, l'applicabilité des techniques de modèle libre proposé pour l'application pratique est démontrée. En outre, certains des régimes de contrôle proposés ont réalisé avec succès un bon compromis entre les objectifs au rotor d’atténuation des vibrations et la minimisation des courants de commande sur une grande plage de fonctionnement.
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Jones, Evan S. "Development of an active damping system to aid in the attitude control of flexible spacecraft." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/26471.
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Defoy, Benjamin. "Investigation on the control of supercritical centrifugal compressors supported by active magnetic bearings : Toward a new control strategy?" Thesis, Lyon, INSA, 2012. http://www.theses.fr/2012ISAL0140/document.
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Le comportement dynamique des turbomachines industrielles doit respecter des critères émis par les normes internationales et les utilisateurs. Les rotors flexibles sont sensibles à la distribution de balourd, et sont soumis aux excitations aérodynamiques de leur environnement. Usuellement, les contrôleurs utilisés peinent à délivrer le niveau d’exigence demandé, par conséquent les propriétés mécaniques des paliers magnétiques sont fortement dépendantes de celles des rotors. L’objectif de ce mémoire est d’analyser le comportement dynamique des compresseurs centrifuges afin de proposer une stratégie de contrôle innovante. D’abord, chaque palier est considéré comme une entité a part entière en couplant ses deux axes d’action. Le comportement dynamique du rotor est exprimé dans le repère polaire. Par ailleurs, la logique floue, qui utilise un modèle de pensée proche du raisonnement humain, applique des actions correctives en fonction du comportement dynamique global du rotor. Ainsi, l’utilisation couplée de ces deux approches créé une synergie permettant d’agir sur le système de manière ciblée. Le contrôleur dissipe l’énergie cinétique du rotor lors du franchissement de vitesses critiques afin d’atténuer la réponse au balourd, ou augmente la raideur du palier lors de vibrations transitoires ou asynchrones afin de réduire la trajectoire du rotor. Le faible amortissement structurel du rotor le rend sensible au phénomène de « spillover » (l’énergie de contrôle affecte les modes de fréquence élevée). Or, la logique floue ne peut pas gérer ce phénomène. Ainsi, un contrôleur PID sous-jacent est utilisé pour maîtriser la stabilité des modes hautes fréquences. Au final, le contrôleur flou polaire permet d’obtenir des marges de performances entre les capacités de cet asservissement et le cahier des charges. Ces marges sont utilisées pour trois objectifs : le respect des spécifications, l’amélioration du comportement subsynchrone, et enfin la simplification et la standardisation du contrôleur sous-jacent nommé ici SPID. Ce contrôleur est tel que ses caractéristiques, dans la plage de fréquence utile, sont indépendantes du rotor pour une application donnée. Enfin, la stratégie développée est évaluée avec des simulations numériques et des essais expérimentaux. D’abord, le modèle numérique est validé, puis le contrôleur est appliqué à un banc d’essais académique. Le comportement est stable et robuste. Il présente des performances supérieures au PID augmenté fourni avec le banc, que ce soit pour la réponse au balourd, ou pour la réponse à des excitations subsynchrones. Finalement, la démarche est appliquée à un compresseur industriel. Les simulations montrent que le comportement est proche de celui exigé pour des machines sur paliers classiques. L’optimisation de l’approche et l’automatisation de la conception pourraient conduire à la standardisation des paliers magnétiques actifs<br>The dynamic behaviour of large turbomachinery should satisfy stringent requirements dictated by international standards and final users. Their flexible rotor is sensitive to the unbalance distribution and subjected to particular excitations coming from the industrial process. Usually, the performance margins between the requirements and the classical controller capabilities are small. Consequently, the magnetic bearing characteristics depend on the rotor geometry. Designing such controllers is difficult and time consuming. The objective of this thesis is to investigate the dynamic behaviour of supercritical centrifugal compressors in order to propose a new control strategy. First, each bearing is considered as one entity by coupling its two axes of action. The introduction of polar quantities permits a better observation of the rotor dynamic behaviour. In addition, by using logic close to human being reasoning, the fuzzy logic modulates the action forces as a function of the global dynamic behaviour. The coupling of the two approaches is an efficient way to apply targeted corrective actions. This controller attenuates the unbalance vibration when crossing critical speeds by applying damping forces, or increases the stiffness during transient or asynchronous excitations in order to limit the maximum displacement reached. As their structural damping is low, flexible rotors are very sensitive to spillover effect, which cannot be managed by fuzzy controllers. Consequently, an underlying PID is necessary. This hand-synthesized controller has high frequency characteristics tuned in order to ensure stability and robustness for each rotor. Compared to a classical approach, the polar fuzzy controller enables to increase the performance margins. These margins are used to fulfil three objectives: the achievement of standards requirements, the improvement of the subsynchronous behaviour, and the simplification and the standardization of the PID controller that we called SPID. This SPID is designed for a given application, such that the bearing characteristics on the operating frequency range are always the same. The control strategy is assessed numerically and experimentally. First, the numerical model is validated with experimental tests. Then, the controller developed is applied to an academic test rig. The controller is stable and robust. It exhibits performance superior to the augmented PID supplied with the test rig for both unbalance response and response to subsynchronous excitations. Finally, the control of an industrial compressor is assessed numerically. The results obtained are close to the standards requirements used for classical bearings. The optimization of the approach and the utilization of an automatic tuning algorithm for high frequency characteristics could lead to the standardization of Active Magnetic Bearings
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Makovec, Kristin Lynne. "A Nonlinear Magnetic Controller for Three-Axis Stability of Nanosatellites." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34131.
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The problem of magnetic control for three-axis stability of a spacecraft is examined. Two
controllers, a proportional-derivative controller and a constant coefficient linear quadratic
regulator, are applied to the system of equations describing the motion of the spacecraft.
The stability of each is checked for different spacecraft configurations through simulations,
and the results for gravity-gradient stable and non gravity-gradient stable spacecraft are
compared. An optimization technique is implemented in an attempt to obtain the best
performance from the controller. For every spacecraft configuration, a set of gains can be
chosen for implementation in the controller that stabilizes the linear and nonlinear equations of motion for the spacecraft.<br>Master of Science
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Tudor, Zdenko. "Design and Implementation of Attitude Control for 3-axes Magnetic Coil Stabilization of a Spacecraft." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for teknisk kybernetikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13273.
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Spacecrafts, especially satellites, play an ever greater rolein our daily lives as we increasingly depend on the services they provide,which in turn, more often than not, critically depend on maintainingcorrect payload attitude. As smaller educational satellites pavethe way for organization, group and privately owned pico-satellites, weexplore the possibilities of attitude control through magnetic coil actuation.We approach the whole problem, from control theory developmentto first prototype actualization and control algorithm implementation,presenting the steps taken in a user-friendly manner while pointing outthe pitfalls and drawbacks of different solutions. The control is based ona dissipative detumbling controller which after the initial phase is overriddenby the reference controller attaining final desired payload attitude.We find that a simple 8-bit, 16Mhz microcontroller unit has the su-cient processing power to continuously compute the geomagnetic fieldusing the complex International Geomagnetic Reference Field model,while simultaneously maintaining correct coil actuation. The powerconsumed by the controllers during the <300 minute control phase,from initial tumbling to desired attitude, given a typical tumbling velocityof absolute magnitude 0.2[rad/sec], is found to be no more than 150Joules across the randomly selected test scenarios. Thus we are able toconclude that three perpendicular magnetic coils, together with constantlypresent disturbances and complex geomagnetic field model preventingit from remaining at an ill-aligned attitude where one actuatingdegree of freedom is lost, provide sufficient actuation for reference controlof a spacecraft.
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Wolfe, Scott Michael. "Small satellite attitude control for sun-oriented operations utilizing a momentum bias with magnetic actuators." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA297796.
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Thesis (M.S. in Electrical Engineering and M.S. in Engineering Science (Astronautics)) Naval Postgraduate School, March 1995.<br>Thesis advisor(s): Titus, Harold A. ; Alfriend, Kyle T. "March 1995." Includes bibliographical references. Also available online.
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Yan, Hui. "Dynamics and real-time optimal control of satellite attitude and satellite formation systems." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4283.
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In this dissertation the solutions of the dynamics and real-time optimal control of
magnetic attitude control and formation flying systems are presented. In magnetic
attitude control, magnetic actuators for the time-optimal rest-to-rest maneuver with a
pseudospectral algorithm are examined. The time-optimal magnetic control is bang-bang
and the optimal slew time is about 232.7 seconds. The start time occurs when the
maneuver is symmetric about the maximum field strength. For real-time computations,
all the tested samples converge to optimal solutions or feasible solutions. We find the
average computation time is about 0.45 seconds with the warm start and 19 seconds with
the cold start, which is a great potential for real-time computations. Three-axis magnetic
attitude stabilization is achieved by using a pseudospectral control law via the receding
horizon control for satellites in eccentric low Earth orbits. The solutions from the
pseudospectral control law are in excellent agreement with those obtained from the
Riccati equation, but the computation speed improves by one order of magnitude. Numerical solutions show state responses quickly tend to the region where the attitude
motion is in the steady state.
Approximate models are often used for the study of relative motion of formation
flying satellites. A modeling error index is introduced for evaluating and comparing the
accuracy of various theories of the relative motion of satellites in order to determine the
effect of modeling errors on the various theories. The numerical results show the
sequence of the index from high to low should be Hill's equation, non- J2, small
eccentricity, Gim-Alfriend state transition matrix index, with the unit sphere approach
and the Yan-Alfriend nonlinear method having the lowest index and equivalent
performance. A higher order state transition matrix is developed using unit sphere
approach in the mean elements space. Based on the state transition matrix analytical
control laws for formation flying maintenance and reconfiguration are proposed using
low-thrust and impulsive scheme. The control laws are easily derived with high
accuracy. Numerical solutions show the control law works well in real-time
computations.
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Robinson, John. "Analysis of the orbit lowering and attitude control performance of a magnetic coil-augmented gossamer sail." Honors in the Major Thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1314.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.<br>Bachelors<br>Engineering and Computer Science<br>Aerospace Engineering
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Wang, Muhao. "H∞ optimal control for linear time invariant and parameter dependent conditions in active magnetic bearing systems." Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.699000.
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Bangert, Philip Verfasser], and Klaus [Gutachter] [Schilling. "Magnetic Attitude Control of Miniature Satellites and its Extension towards Orbit Control using an Electric Propulsion System / Philip Bangert ; Gutachter: Klaus Schilling." Würzburg : Universität Würzburg, 2019. http://d-nb.info/1181693691/34.
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Pesch, Alexander Hans. "Development of Chatter Attenuation Robust Control for an AMB Machining Spindle." Cleveland State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=csu1401198790.
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Wroblewski, Adam C. "Model Identification, Updating, and Validation of an Active Magnetic Bearing High-Speed Machining Spindle for Precision Machining Operation." Cleveland State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=csu1318379242.
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Sabirin, Chip Rinaldi [Verfasser]. "Digital Control for Active Magnetic Bearings in High-Speed Permanent-Magnet Synchronous Machine with 40000 rpm and 40 kW / Chip Rinaldi Sabirin." Aachen : Shaker, 2014. http://d-nb.info/106619789X/34.
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Kolařík, František. "Řídicí systém aktivního magnetického ložiska." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229668.
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Thesis deals with active magnetic bearing (AMB) levitation control design. Its prototype was done in FSI collaboration with FEKT VUT Brno. The research is focused on communication tools and mathematical model making as well as general AMB issues. Based on this the control design is done an experimentally verified.
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Gonçalves, Junior Romildo [UNESP]. "Controle ativo de vibração de rotores com mancais magnéticos: influência da flexibilidade dos rotores." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/94539.
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Made available in DSpace on 2014-06-11T19:27:14Z (GMT). No. of bitstreams: 0
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goncalvesjr_r_me_ilha.pdf: 1793490 bytes, checksum: 31bd12dfbef20fead2490b33aa2d1148 (MD5)<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Este trabalho apresenta uma análise teórica do desempenho de um sistema de controle ativo de vibração de rotores utilizando mancais magnéticos. O esquema de controle ativo proposto utiliza a estratégia de controle ativo feedforward sobreposta ao sistema de controle feedback dos mancais magnéticos. O desempenho desse sistema de controle foi analisado em função da flexibilidade dos rotores considerando o impacto do número e da localização dos atuadores e dos sensores de erro sobre a redução dos níveis de vibração desses rotores, tanto em termos de vibração global quanto em termos de vibração local. O sistema de controle foi aplicado em um modelo teórico de rotor desenvolvido através do método da matriz de impedância.<br>This work presents a theoretical analysis of the performance of a system of active control of rotor vibrations using magnetic bearings. The proposed scheme of active control uses a feedforward active control strategy superimposed on the feedback control system of the magnetic bearings. The performance of this control system was analyzed as a function of the rotor flexibility considering the impact and optimization of the actuators and error sensors placement on the reduction of vibration levels of these rotors, in terms of global vibration as well as in terms of local vibration of the rotor. The control system was applied to a theoretical rotor model developed by the matrix impedance method.
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Kulick, Wayne J. "Development of a Control Moment Gyroscope controlled, three axis satellite simulator, with active balancing for the bifocal relay mirror initiative." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FKulick.pdf.
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Martens, Bas. "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." Master's thesis, Faculty of Engineering and the Built Environment, 2019. https://hdl.handle.net/11427/31621.
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Active spacecraft attitude control by using a pumped fluid as 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 dissertation, a parametric sizing model is developed that can optimize a fluid loop for any mission, based on pump capabilities and customer requirements. The model can be applied to circular, square and helical fluid loops, and includes the power consumption due to viscous friction. A configurable prototype was developed to verify the model, as well as a spherical air bearing to verify the rotational aspects of the various fluid loop configurations. The model was applied to various hypothetical missions. In conclusion, the fluid loop has the fundamental potential to replace reaction wheels in a wide variety of satellites above approximately 20 kg, if mass is carefully optimized and efforts are made to develop a suitable pump. This is considered worthwhile, as the actuator comes with many potential advantages.
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Aucamp, Christiaan Daniël. "Model predictive control of a magnetically suspended flywheel energy storage system / Christiaan Daniël Aucamp." Thesis, North-West University, 2012. http://hdl.handle.net/10394/8601.
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The goal of this dissertation is to evaluate the effectiveness of model predictive control (MPC)
for a magnetically suspended flywheel energy storage uninterruptible power supply (FlyUPS).
The reason this research topic was selected was to determine if an advanced control technique
such as MPC could perform better than a classical control approach such as decentralised
Proportional-plus-Differential (PD) control.
Based on a literature study of the FlyUPS system and the MPC strategies available, two MPC
strategies were used to design two possible MPC controllers were designed for the FlyUPS,
namely a classical MPC algorithm that incorporates optimisation techniques and the MPC
algorithm used in the MATLAB® MPC toolbox™. In order to take the restrictions of the system
into consideration, the model used to derive the controllers was reduced to an order of ten
according to the Hankel singular value decomposition of the model.
Simulation results indicated that the first controller based on a classical MPC algorithm and
optimisation techniques was not verified as a viable control strategy to be implemented on the
physical FlyUPS system due to difficulties obtaining the desired response. The second
controller derived using the MATLAB® MPC toolbox™ was verified to be a viable control
strategy for the FlyUPS by delivering good performance in simulation.
The verified MPC controller was then implemented on the FlyUPS. This implementation was
then analysed in order to validate that the controller operates as expected through a
comparison of the simulation and implementation results. Further analysis was then done by
comparing the performance of MPC with decentralised PD control in order to determine the
advantages and limitations of using MPC on the FlyUPS.
The advantages indicated by the evaluation include the simplicity of the design of the controller
that follows directly from the specifications of the system and the dynamics of the system, and
the good performance of the controller within the parameters of the controller design. The
limitations identified during this evaluation include the high computational load that requires a
relatively long execution time, and the inability of the MPC controller to adapt to unmodelled
system dynamics.
Based on this evaluation MPC can be seen as a viable control strategy for the FlyUPS, however
more research is needed to optimise the MPC approach to yield significant advantages over
other control techniques such as decentralised PD control.<br>Thesis (MIng (Computer and Electronic Engineering))--North-West University, Potchefstroom Campus, 2013