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1
Townsend, Shane Martin Joseph. "Non-linear model predictive control". Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301061.
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Neff, Andrew. "Linear and non-linear control of a quadrotor UAV". Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1181251774/.
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Mhana, Khalid Jalal. "Optimal control of non-linear systems". Thesis, University of Sheffield, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412720.
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Pechev, Alexandre Nikolov. "Robust linear and non-linear control of magnetically levitated systems". Thesis, Cardiff University, 2004. http://orca.cf.ac.uk/55944/.
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The two most advanced applications of contactless magnetic levitation are high-speed magnetic bearings and magnetically levitated vehicles (Maglev) for ground transportation using superconducting magnets and controlled d.c. electromagnets. The repulsion force from superconducting magnets provide stable levitation with low damping, while the suspension force generated by electromagnets is inherently unstable. This instability, due to the in verse force-distance relationship, requires the addition of feedback controllers to sustain stable suspension. The problem of controlling magnetically levitated systems using d.c. electromagnets under different operating conditions has been studied in this thesis with a design process primarily driven by experimental results from a representative single-magnet test rig and a multi-magnet vehicle. The controller-design stages are presented in detail and close relationships have been constructed between selection of performance criteria for the derivation process and desired suspension characteristics. Both linear and nonlinear stabilising compensators have been developed. Simulation and experimental results have been studied in parallel to assess operational stability and the main emphasis has been given to assessing performance under different operational conditions. For the experimental work, a new digital signal processor-based hardware platform has been designed, built with interface to Matlab/Simulink. The controller design methods and algorithmic work presented in this thesis can be divided into: non-adaptive, adaptive, optimal linear and nonlinear. Adaptive algorithms based on model reference control have been developed to improve the performance of the suspension system in the presence of considerable variations in external payload and force disturbances. New design methods for Maglev suspension have been developed using robust control theory (%oo and fi synthesis). Single- and multi-magnet control problems have been treated using the same framework. A solution to the Hoo controller-optimisation problem has been derived and applied to Maglev control. The sensitivity to robustness has been discussed and tools for assessing the robustness of the closed-loop system in terms of sustaining stability and performance in the presence of uncertainties in the suspension model have been presented. Multivariable controllers based on %00 and /i synthesis have been developed for a laboratory scale experimental vehicle weighing 88 kg with four suspension magnets, and experimental results have been derived to show superiority of the proposed design methods in terms of ability to deal with external disturbances. The concept of Hoo control has been extended to the nonlinear setting using the concepts of energy and dissipativity, and nonlinear state-feedback and out put-feed back controllers for Maglev have been developed and reported. Simulation and experimental results have been presented to show the improved performance of these controllers to attenuate guideway-induced disturbances while maintaining acceptable suspension qualities and larger operational bandwidth.
5
Petridis, Anthemios Philemon. "Non-linear robust control of S.I. engines". Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.399231.
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Hong, Tao. "Non-linear predictive control of chemical processes". Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245078.
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Baek, Kwang-Hyun. "Non-linear optimisation problems in active control". Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243131.
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Ganapathy, Annadurai Shathiyakkumar. "Non-Linear Electromechanical System Dynamics". ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1799.
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Electromechanical systems dynamics analysis is approached through nonlinear differential equations and further creating a state space model for the system. There are three modules analyzed and validated, first module consists two magnet coupled with a mass spring damper system as a band-pass system, Low-pass equivalent system and Low-pass equivalent system through perturbation analysis. Initially Band Pass frameworks for the systems are formulated considering the relation between the mechanical forcing and current. Using Mathematical tools such as Hilbert transforms, Low-Pass equivalent of the systems are derived. The state equations of the systems are then used to design a working model in MATLAB and simulations investigated completely. The scope of the modules discussed for further development of tools various applications.
9
Yung, K. L. "Microprocessor based non-linear adaptive controller". Thesis, University of Plymouth, 1985. http://hdl.handle.net/10026.1/2492.
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The advent of microprocessors has created the possibility of developing low cost adaptive controllers for small process plants which in the past badly needed but could not afford such controllers. To examine the practicality of developing advanced low cost microprocessor based controller, this thesis describes the development of a non-linear adaptive controller for a nylon crimping plant which is a typical example of small process plants. In order to test the algorithm on site, an algorithm development/implement device basing on a novel multi-tasking concept was developed. This novel microprocessor based device can perform program development, on-line algorithm test and data logging at the same time, while, still maintaining its small size for easy transportation. When the control algorithm was fully developed and tested, a low cost dedicated controller using an Intel 8085 processor was designed to house the algorithm and as a direct replacement of the original analogue controller.
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Fontes, Fernando Armenio Da Costa Castro. "Optimisation-based control of constrained non linear systems". Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299453.
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Syre, Terese Vardenær. "Anti-Slug Control with Non-Linear State Estimation". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for teknisk kybernetikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18378.
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In offshore production, the two-phase mixture of oil and gas is transported from the seabed oil wells to the surface facilities by pipelines and risers. The two-phase flow can have different flow regimes, where severe slugging is one undesirable flow regime and an effective solution is needed to prevent it. The recommended solution is active control of the top-side choke valve. Previously, controllability analysis is done of two-phase flow in a 4-state pipeline-riser model. This analyze concludes that the best way to control the choke valve is by using the subsea pressure measurement combined with topside flow measurement. However, the subsea pressure might be difficult to measure correctly because the pipeline is placed under tough conditions, hundredth or even thousands of meters under sea level. One possibility is to combine topside pressure with topside flow measurement and use for estimation of states or other sub-sea measurements that are normally not available. Simulation studies are done in MATLAB of different anti-slug control solutions. Linear Kalman filter, extended Kalman filter (EKF) and unscented Kalman filter (UKF) are used for state estimation and combined with controllers such as PI, LQR and MPC. The input to the system is flow rate of gas and liquid, and the nominal choke opening. The input disturbance to the process is change in the flow rate of gas and liquid imitating slug flow.As expected, when only topside measurements are used, because of the highly nonlinear system dynamics the linear Kalman filter fails in stabilizing the system. The EKF works good when the system has low input disturbance, while the UKF is the best nonlinear filter when the system has high input disturbance. However, when the nominal choke opening is increased, the UKF combined with a controller fails. The LQR controller combined with UKF shows slightly better results than the PI and MPC controller combined with the same filter for state estimation. There is also potential in using the high-gain observer in control strategies.
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Tan, Woei Wan. "Self-learning neurofuzzy control of non-linear systems". Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364037.
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Narciso, Diogo Alexandre Cipriano. "Developments in non linear multiparametric programming and control". Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511281.
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Dysenius, Hannah. "Non-Linear Automatic Control of Autonomous Lawn Mower". Thesis, Linköpings universitet, Reglerteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-129116.
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This master thesis contains modeling and nonlinear automatic control of an autonomous lawn mower. The vehicle shall be able to follow a magnetic field loop buried in the lawn on an arbitrary distance, including straddling. A unicycle model of the lawn mower has been derived based on previous work. The model holds for the assumption of non slip environment. Two diff erent control strategies have been implemented and evaluated in this thesis. One is based on feedback linearization and with the feedback gain estimated using an LQ-controller. The other strategy is based on linearization at an equilibrium point and also with the use of an LQ-controller. The only state that can be measured is the distance to the magnetic loop. In order to estimate the other states, an observer has been implemented using the linearized in an equilibrium point model and a Kalman filter. The navigation of the autonomous lawn mower is performed using a magnetic loop buried in the lawn. The non-linearity of the magnetic field causes diffi culties when estimating the distance to the loop. One magnetic field strength corresponds to two distances to the magnetic loop. The nature of the magnetic field and the measurement noise causes the precision of the controller to be limited. The conclusion of this master thesis is that it is possible to navigate and follow the magnetic loop at a distance greater than 0.3 [m], but with overshoots during sharp turns. If the reference distance is smaller than that, the behavior of the robot will be oscillating when following the loop. The limitations of the controller performance is due to the lack of information which can be extracted from the measurements of the magnetic field.
15
Haynes, Barry P. "A neural network adaptive controller for non-linear systems". Thesis, University of Portsmouth, 1997. https://researchportal.port.ac.uk/portal/en/theses/a-neural-network-adaptive-controller-for-nonlinear-systems(19584462-246e-4de3-9e80-cda4923a38c1).html.
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Castaneda, Veimar Yobany Moreno. "Transmission line modelling applied to non-linear control systems". Thesis, University of Huddersfield, 2006. http://eprints.hud.ac.uk/id/eprint/17872/.
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Dutka, Arkadiusz Stanisław. "Non-linear identification, estimation and control of automotive powertrains". Thesis, University of Strathclyde, 2005. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24339.
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Increasingly tight emission regulations put a pressure on control engineers to come up with improved engine control systems. The task is difficult, as it is desired to minimize complexity, cost and maximize reliability and performance, all at the same time. Fortunately, modern control techniques offer assistance in achieving these goals. This motivation resulted in a range of topics developed in this thesis. A modelling, estimation and fault detection theory is presented. The estimation theory is often used for the system identification, but its main application is the model-based filtering, so important in real systems. The real systems are subject to failures. A theoretical development of the fault detection algorithm for non-linear systems is presented. The emphasis moves then to the control algorithms design. The non-linear algorithms based on the state-dependent model structure are introduced. An extension of the state-dependent Riccati equation method with a future trajectory prediction is developed. Also, the non-linear version of generalized predictive control algorithm is presented. Optimality of solutions is analyzed and corrections to algorithms are introduced to preserve the optimality. The theory needs practical verification. The identification of the spark ignition engine is presented next. A datadriven system identification method is developed. It provides an accurate model for control design purposes. The predictive control algorithm design is presented next. A simple air-fuel ratio control as well as a full multivariable control system design, with a torque as an output, is introduced. Improved tracking and tighter air-fuel ratio regulation is achieved. The control system efficiency may be impaired by the system noise and the model uncertainty. For that reason the model-based estimation techniques are very important. It is demonstrated that not only the noise immunity, but also robustness is significantly improved when Kalman filtering methods are employed. Last important topic of fault diagnosis is then presented. Faults must be detected, isolated and identified to enable successful control system re-configuration.
18
Dimopoulos, Konstantinos Panagiotis. "Non-linear control strategies using input-state network models". Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340027.
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Gu, D. W. "Design of non-linear control systems via mathematical programming". Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37714.
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Benomair, Abdollha. "Non-linear observer based control of magnetic levitation systems". Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/20582/.
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Active magnetic levitation AML systems have been widely used in magnetic levitation vehicles, wind turbine, medical applications, micro robot actuation and turbo-machinery. Contactless support of objects continues to be a fantasy for several centuries. The utilization of magnetic forces seems to be the ideal solution in many situations to such a goal. Using magnetic forces to support an object without any mechanical contact is constrained by the laws of magnetism. Earnshaw’s theorem states that when the inverse-square-law forces govern several charged particles, they can never be within a stable equilibrium. The interaction between ferromagnetic objects and electromagnets of either the active or passive type, is associated with an unstable nature. This unstable behaviour can be represented by highly non-linear differential equations. In the literature many researches are based on linearised models around a specific nominal operating point then linear controller is utilized to control the system. The associated problem with the linear control technique is that the system only be adequately controlled in a small region around the equilibrium point but the variation of operating regions in such non-linear system is wide following a major disturbance. In this research, two kinds of non-linear observer-based excitation controller are proposed for Maglev to ensure the stability of non-linear system in the presence of large disturbance and over larger operation regions. A combination of full-order Nonlinear high-gain observer (NHGO) with LQR-feedback linearisation is considered as first proposal. Second proposed controller is based on the Lyapunov stability theorems, and a further non-linear full-order observer-based controller via a non-linear fuzzy sliding mode controller is developed for Maglev system. The proposed control approaches are tested and validated through simulated exercises of a magnetic levitation system. Comparative assessments of the approaches are presented and discussed through the thesis.
21
Vaudrey, Michael Allen. "Adaptive Control Methods for Non-Linear Self-Excited Systems". Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/28884.
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Self-excited systems are open loop unstable plants having a nonlinearity that prevents an exponentially increasing time response. The resulting limit cycle is induced by any slight disturbance that causes the response of the system to grow to the saturation level of the nonlinearity. Because there is no external disturbance, control of these self-excited systems requires that the open loop system dynamics are altered so that any unstable open loop poles are stabilized in the closed loop.
This work examines a variety of adaptive control approaches for controlling a thermoacoustic instability, a physical self-excited system. Initially, a static feedback controller loopshaping design and associated system identification method is presented. This design approach is shown to effectively stabilize an unstable Rijke tube combustor while preventing the creation of additional controller induced instabilities. The loopshaping design method is then used in conjunction with a trained artificial neural network to demonstrate stabilizing control in the presence of changing plant dynamics over a wide variety of operating conditions. However, because the ANN is designed specifically for a single combustor/actuator arrangement, its limited portability is a distinct disadvantage.
Filtered-X least mean squares (LMS) adaptive feedback control approaches are examined when applied to both stable and unstable plants. An identification method for approximating the relevant plant dynamics to be modeled is proposed and shown to effectively stabilize the self-excited system in simulations and experiments. The adaptive feedback controller is further analyzed for robust performance when applied to the stable, disturbance rejection control problem. It is shown that robust stability cannot be guaranteed because arbitrarily small errors in the plant model can generate gradient divergence and unstable feedback loops.
Finally, a time-averaged-gradient (TAG) algorithm is investigated for use in controlling self-excited systems such as the thermoacoustic instability. The TAG algorithm is shown to be very effective in stabilizing the unstable dynamics using a variety of controller parameterizations, without the need for plant estimation information from the system to be controlled.Ph. D.
22
Eaton, Mark Taylor. "Non-linear state estimation and control of emulsion polymerization /". Thesis, Connect to this title online; UW restricted, 1995. http://hdl.handle.net/1773/9901.
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Godasi, Satyam. "Identification and control of non-linear distributed parameter systems /". For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2002. http://uclibs.org/PID/11984.
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Jia, Feng. "Application of linear and non-linear principal component analysis in multivariate statistical process control". Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311152.
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VERRELLI, CRISTIANO MARIA. "NON LINEAR CONTROL DESIGN FOR INDUCTION MOTORS AND SYNCHRONOUS GENERATORS". Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2005. http://hdl.handle.net/2108/179.
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La tesi presenta recenti sviluppi nel progetto di leggi di controllo non lineari per motori ad induzione e generatori sincroni: tecniche di controllo robuste, adattative, in retroazione dallo stato o dall'uscita sono utilizzate per tali sistemi elettromeccanici descritti da equazioni differenziali ordinarie, deterministiche e
¯nito-dimensionali e possibilmente caratterizzati da incertezze come parametri non noti (costanti o tempovarianti).
I motori ad induzione, che, grazie alla loro più semplice struttura, sono più affidabili e meno costosi di quelli a magneti permanenti, a riluttanza variabile e in corrente continua, sono difficili da controllare per diverse ragioni: le dinamiche sono intrinsecamente non lineari e multivariabile (due ingressi di controllo e due uscite da controllare) ; non tutte le variabili di stato e non tutte le uscite da controllare possono essere disponibili per la retroazione; sono presenti parametri critici incerti, come la coppia di carico, tipicamente non nota in tutti i motori elettrici e la resistenza rotorica, che può variare fino al 100 % durante il funzionamento a causa del riscaldamento del rotore. La disponibilità di potenti DSP a basso costo e i
progressi nell'elettronica di potenza hanno reso algoritmi complessi implementabili anche per motori ad induzione di media e piccola taglia, che, in tal modo, sono effettivamente in grado di sostituire i motori elettrici usati, ammesso che siano garantite alte prestazioni dinamiche ed elevata e±cienza: ciò ha motivato intensi sforzi di ricerca nel progetto di controllori non lineari per motori ad induzione.
In modo analogo, la stabilizzazione transitoria e la regolazione della tensione per sistemi di potenza sono problemi di controllo classicamente di±cili: tutti i modelli dinamici che sono stati proposti per una singola macchina connessa a un in ¯ n ite bu s mostrano una intrinseca natura non lineare e, di conseguenza, diversi punti di equilibrio stabili e instabili. Primi studi miravano alla determinazione di regioni di stabilità delle condizioni operative desiderate, via funzioni di Lyapunov, cosi da studiare l'effetto delle improvvise perturbazioni meccaniche e elettriche che possono destabilizzare il sistema e forzare il singolo generatore
ad essere disconnesso dalla rete. Il problema consiste dunque nel mantenere la velocità del generatore prossima alla velocità sincrona quando perturbazioni occorrono (stabilizzazione transitoria) e regolare la tensione di uscita al corrispondente valore di riferimento nel caso di perturbazioni costanti e permanenti (regolazione della tensione in uscita). A tal riguardo, i controllori lineari realmente impiegati, progettati sulla base di approssimazioni lineari attorno alle condizioni operative, non sono in grado di sostenere le forti perturbazioni che tipicamente occorrono nei sistemi di potenza: controllori non lineari sono di conseguenza
richiesti.
La tesi è suddivisa in due parti: la prima parte (motore ad induzione) è formata dai capitoli 2, 3 e 4, mentre la seconda parte (generatore sincrono) consiste dei capitoli 5 e 6. I capitoli 2 e 3 affrontano il problema del controllo di motori ad induzione senza sensore di velocità: l'esistenza di uno schema di controllo globale è esplorata nel capitolo 2 mentre una legge di controllo non lineare adattativa è progettata nel capitolo 3. Il capitolo 4 è dedicato al progetto di un controllore non lineare per motori ad induzione
sen so rless: uno schema di controllo in retroazione dall'uscita è proposto. I capitoli 5 e 6 concernono il problema del controllo di un generatore sincrono con incertezze nei parametri: nel capitolo 5, un controllore non lineare robusto adattativo è presentato per la stabilizzazione transitoria, mentre il capitolo 6 propone
una legge di controllo non lineare robusta adattativa che garantisce sia stabilizzazione transitoria che regolazione della tensione in uscita.The thesis incorporates recent advances in the design of nonlinear control laws for induction motors and synchronous generators: robust, adaptive, state or output feedback control techniques are used for both these electro-mechanical systems which are modelled by ¯nite dimensional, deterministic ordinary differential equations and are possibly affected by uncertainties, such as unknown constant and time-varying parameters. Induction motors, which, due to their simpler construction, are more reliable and less expensive than those permanent magnet, switched reluctance and d.c. motors are di±cult to control for several reasons: their dynamics are intrinsically nonlinear and multivariable (two control inputs and two outputs to be controlled); not all of the state variables and not all of the outputs to be controlled may be available for feedback; there are critical uncertain parameters such as load torque, which is typically unknown in all electrical drives, and rotor resistance, which, due to rotor heating, may vary up to 100% during operations. The availability of low cost powerful digital signal processors and advances in power electronics made complex algorithms implementable even for medium- and small-size induction motors, which, in this way, could replace currently used motors provided that high dynamic tracking performance along with highpower efficiency are achieved: this is what motivated intense research efforts in induction motor control design. In analogous way, transient stabilization and voltage regulation for power systems are classically difficult control problems: all the dynamic models which have been developed for a single machine connected to an in¯nite bus show an intrinsic nonlinear nature and, consequently, there are several stable and unstable equilibrium points. Early studies aimed at determining the stability regions of desired operating conditions by means of Lyapunov functions in order to study the effect of perturbations. In fact, sudden mechanical and electrical perturbations may drive the system outside its stability region and force the generator to be disconnected from the network. The transient stabilization and voltage regulation problem consists in the design of an excitation control which keeps the generator speed close to the synchronous speed when perturbations occur (transient stabilization) and regulates the output voltage to the corresponding reference value in the case of permanent constant perturbations (voltage regulation). To this purpose, linear controllers are actually employed which are designed on the basis of linear approximations around operating conditions: only small perturbations and deviations from operating conditions can be handled. It is clear that nonlinear controllers are required to handle the large perturbations that typically occur in power systems. The thesis is divided into two parts: Part I (induction motor) consists of Chapters 2, 3 and 4 while Part II (synchronous generator) consists of Chapters 5 and 6. Chapters 2 and 3 address the problem of controlling a speed-sensorless induction motor: the existence of a global controller is explored in Chapter 2, while a nonlinear adaptive control scheme is developed in Chapter 3. Chapter 4 is devoted to nonlinear control design for a sensorless induction motor: an output feedback control algorithm is proposed. Chapters 5 and 6 address the problem of controlling a synchronous generator with parameter uncertainty: a nonlinear robust adaptive transient stabilizing control is presented in Chapter 5, while Chapter 6 proposes a nonlinear robust adaptive transient stabilizing and output regulating control algorithm.
26
Korsfeldt, Larsén Alexander. "Non-linear Model Predictive Control for space debris removal missions". Thesis, Luleå tekniska universitet, Rymdteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-72049.
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The rapidly increasing amounts of space debris orbiting Earth is threatening to reach a critical level, where the near-Earth environment becomes so overfilled with junk that many missions simply become unfeasible. Long-term active debris removal operations appear to be a necessity, but due to the scale of the problem this will likely be an expensive affair spanning decades or even centuries. Many of the mission-related costs can be significantly reduced by making use of a smaller spacecraft, such as the rapidly developing CubeSat standard. An issue with this approach is the limited actuation capabilities, as that makes it very difficult to perform orbital maneuvers in a fuel-efficient manner. Rather than making a few high-impulse thrusts over the course of the mission, the thrust must be applied continuously for several hundred hours. This thesis attempts to solve the problem by using a non-linear Model Predictive Control strategy to implement an Orbital and Attitude Control system for a small satellite. This was done in MATLAB, using the fast-NMPC package MATMPC recently developed by Yutao Chen at Padova University. The controller was tested in a realistic model of the near-Earth environment, where disturbances such as drag and gravitational perturbations are simulated. It was shown through simulations that this method can successfully be used to perform a fuel-efficient rendezvous maneuver with an uncontrollable object, a critical step in any Active Debris Removal operation. Using a 4 kg CubeSat with a 30 µN thruster mounted on each of its six surfaces, the total mass consumption for a phasing maneuver of 10 degrees at 300 km altitude was less than 0.1% of the spacecraft mass. This assumes an Isp of 1,150 s, which is the specific impulse of the S-iEPS Electrostatic thruster flown on the Aero-Cube-8 IMPACT mission. This is made possible through prediction horizons spanning several days, which in turn forces the controller to operate at sampling rates as low as 1/100 Hz due to the computational load. Fully realizing the potential of this technique would likely require the inclusion of a low-level controller that uses the generated trajectories as input values, as this would negate many of the issues associated with a heavy computational load. The urgency of the space debris problem, and the endless list of other CubeSat applications that would benefit from a flexible and fuel-efficient AOCS, makes this an interesting to topic to consider for further research.
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Karlsson, Mia. "Control of Unmanned Aerial Vehicles using Non-linear Dynamic Inversion". Thesis, Linköping University, Department of Electrical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1519.
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This master's thesis deals with the control design method called Non-linear Dynamic Inversion (NDI) and how it can be applied to Unmanned Aerial Vehicles (UAVs). In this thesis, simulations are conducted using a model for the unmanned aerial vehicle SHARC (Swedish Highly Advanced Research Configuration), which Saab AB is developing.
The idea with NDI is to cancel the non-linear dynamics and then the system can be controlled as a linear system. This design method needs much information about the system, or the output will not be as desired. Since it is impossible to know the exact mathematical model of a system, some kind of robust control theory is needed. In this thesis integral action is used.
A problem with NDI is that the mathematical model of a system is often very complex, which means that the controller also will be complex. Therefore, a controller that uses pure NDI is only discussed, and the simulations are instead based on approximations that use a cascaded NDI. Two such methods are investigated. One that uses much information from aerodata tables, and one that uses the derivatives of some measured outputs. Both methods generate satisfying results. The outputs from the second method are more oscillatory but the method is found to be more robust. If the signals are noisy, indications are that method one will be better.
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Arvidsson, Marcus, i Daniel Karlsson. "Attenuation of Harmonic Distortion in Loudspeakers Using Non-linear Control". Thesis, Linköpings universitet, Reglerteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-78645.
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The first loudspeaker was invented almost 150 years ago and even though much has changed regarding the manufacturing, the main idea is still the same. To produce clean sound, modern loudspeaker consist of expensive materials that often need advanced manufacturing equipment. The relatively newly established company Actiwave AB uses digital signal processing to enhance the audio for loudspeakers with poor acoustic properties. Their algorithms concentrate on attenuating the linear distortion but there is no compensation for the loudspeakers' non-linear distortion, such as harmonic distortion. To attenuate the harmonic distortion, this thesis presents controllers based on exact input-output linearisation. This type of controller needs an accurate model of the system. A loudspeaker model has been derived based on the LR-2 model, an extension of the more common Thiele-Small model. A controller based on exact input-output linearisation also needs full state feedback, but since feedback risk being expensive, state estimators were used. The state estimators were based on feed-forward or observers using the extended Kalman filter or the unscented Kalman filter. A combination of feed-forward state estimation and a PID controller were designed as well. In simulations, the total harmonic distortion was attenuated for all controllers up to 180 Hz. The simulations also showed that the controllers are sensitive to inaccurate parameter values in the loudspeaker model. During real-life experiments, the controllers needed to be extended with a model of the used amplifier to function properly. The controllers that were able to attenuate the harmonic distortion were the two methods using feed-forward state estimation. Both controllers showed improvement compared to the uncontrolled case for frequencies up to 40 Hz.
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Abdulaziz, Ali Ahmed. "Neural-based controller development for solving non-linear control problems". Thesis, University of Newcastle Upon Tyne, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260976.
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Rokni, Lamooki Gholam Reza. "Adaptive and non-linear control : bifurcation, computation and partial stabilisation". Thesis, University of Exeter, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288369.
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Richardson, Thomas Stuart. "Continuation methods applied to non linear flight dynamics and control". Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268783.
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SPINOLA, ALEXANDRE DE LIMA. "MODELING AND NON LINEAR CONTROL OF A GROUND VEHICLENULLS STEERING". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=5109@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORModelagem e Controle Não Linear de um Veículo Terrestre sobre Suspensão descreve um estudo em dinâmica veicular no qual inicialmente apresenta-se um modelo analítico para representar a geração de forças longitudinais e laterais no contato do pneu com o solo. Em seguida é desenvolvido, para um automóvel de passeio terrestre sobre suspensão, um modelo não linear de 4 graus de liberdade (velocidades longitudinal, lateral, de guinada e de rolagem), e a sua linearização. Expande-se esse modelo para um de 8 graus de liberdade, no qual inclui-se o movimento de rotação axial de cada uma das quatro rodas, e consideram-se os movimentos do veículo somente no plano, sem efeitos de pitch ou bounce, mas apresentando alguma relação de distribuição de cargas devido ao roll. Descrevem-se ainda modelos em Grafos de Ligação para os três dinâmicas de um veículo terrestre (longitudinal, lateral e vertical) e seus acoplamentos, visando futuras análises mais detalhadas desse sistema. Todos os modelos em malha aberta são validados através simulações computacionais em diversas condições típicas de operação. Na segunda parte desse trabalho é apresentada a estratégia proposta para o tratamento do problema de controle direcional do veículo em uma manobra qualquer, empregando a metodologia da linearização por realimentação, tendo como base o modelo linear de 4 graus de liberdade. São analisados os resultados encontrados através de simulação computacional para a malha fechada com diferentes combinações de parâmetros, empregando os modelos não lineares de 4 e 8 graus de liberdade. Conclui-se discutindo a possibilidade de generalização deste procedimento para diferentes aplicações em Dinâmica Veicular.
Modeling and Non Linear Control of a Ground Vehicle's Steering describles a study in vehicle dynamics, which presents an analytic model representing the generation of longitudinal and lateral forces at the contact patch between tire and ground. Next it is developed, for a typical passenger car, a non-linear model with four degrees of freedom (longitudinal, lateral, yaw and roll velocities), and its linearization. This model is then expanded to another one with eight degrees of freedom, which includes the axial rotation of each one of the four wheels, and considers the vehicle's movement only at a known plane, whithoud pitch and bounce effects, but including some load distribution among the wheels, due to roll. Computational simulation in varius typical operation condition validate all open loop models. The second part of this work presents the proposed strategy for directional control of a vehicle at any type of manoeuvre, using the feedback linearization methodology, directly applied to the linear four degrees of freedom model. Theresults obtained trhough computational simulation for a closed loop model with different parameters are analysed using both nonlinear four and eight degrees of freedom models. The possibility of generalizing this procedure to distinct applications in Vehicle Dynamics is, then, discussed.
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Mohamed, Ramadan Haitham Saad. "Non-linear control and stabilization of VSC-HVDC transmission systems". Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112046/document.
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L'intégration des liaisons à courant continu dans les systèmes électriques permet d’accroitre les possibilités de pilotage des réseaux, ce qui permet d’en améliorer la sûreté et de raccorder de nouveaux moyens de production. Pour cela la technologie VSC-HVDC est de plus en plus plébiscitée pour interconnecter des réseaux non synchrones, raccorder des parcs éoliens offshore, ou contrôler le flux d’énergie notamment sur des longues distances au travers de liaisons sous-marines (liaison NorNed). Les travaux de cette thèse portent sur la modélisation, la commande non-linéaire et la stabilisation des systèmes VSC–HVDC, avec deux axes de travail. Le premier se focalise sur la conception et la synthèse des lois de commandes non-linéaires avancées basées sur des systèmes de structures variables (VSS). Ainsi, les commandes par modes glissants (SMC) et le suivi asymptotique de trajectoire des sorties (AOT) ont été proposées afin d’assurer un degré désiré de stabilité en utilisant des fonctions de Lyapunov convenables. Ensuite, la robustesse de ces commandes face à des perturbations et/ou incertitudes paramétriques a été étudiée. Le compromis nécessaire entre la robustesse et le comportement dynamique requis dépend du choix approprié des gains. Ces approches robustes, qui sont facile à mettre en œuvre, ont été appliquées avec succès afin d’atteindre des performances dynamiques élevées et un niveau raisonnable de stabilité vis-à-vis des diverses conditions anormales de fonctionnement, pour des longueurs différentes de liaison DC. Le deuxième vise à étudier l’influence de la commande du convertisseur VSC-HVDC sur l'amélioration de la performance dynamique du réseau de courant alternatif en cas d’oscillations. Après une modélisation analytique d’un système de référence constitué d’un groupe connecté à un convertisseur VSC-HVDC via un transformateur et une ligne, un contrôleur conventionnel simple PI est appliqué au niveau du convertisseur du système pour agir sur les oscillations rotoriques de la machine synchrone. Cette commande classique garantie une amélioration acceptable des performances dynamiques du système; surtout pour l'amortissement des oscillations de l'angle de puissance de la machine synchrone lors de défautsThe integration of nonlinear VSC-HVDC transmission systems in power grids becomes very important for environmental, technical, and economic reasons. These systems have enabled the interconnection of asynchronous networks, the connection of offshore wind farms, and the control of power flow especially for long distances. This thesis aims the non-linear control and stabilization of VSC-HVDC systems, with two main themes. The first theme focuses on the design and synthesis of nonlinear control laws based on Variable Structure Systems (VSS) for VSC-HVDC systems. Thus, the Sliding Mode Control (SMC) and the Asymptotic Output Tracking (AOT) have been proposed to provide an adequate degree of stability via suitable Lyapunov functions. Then, the robustness of these commands has been studied in presence of parameter uncertainties and/or disturbances. The compromise between controller’s robustness and the system’s dynamic behavior depends on the gain settings. These control approaches, which are robust and can be easily implemented, have been applied to enhance the system dynamic performance and stability level in presence of different abnormal conditions for different DC link lengths. The second theme concerns the influence of VSC-HVDC control on improving the AC network dynamic performance during transients. After modeling the Single Machine via VSC-HVDC system in which the detailed synchronous generator model is considered, the conventional PI controller is applied to the converter side to act on damping the synchronous machine power angle oscillations. This simple control guarantees the reinforcement of the system dynamic performance and the power angle oscillations damping of the synchronous machine in presence of faults
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Ajlouni, Naim. "Genetic algorithms for control system design". Thesis, University of Salford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308088.
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Herrmann, Guido. "Discretization of non-linear controls with application to robust, sliding-mode-based control systems". Thesis, University of Leicester, 2000. http://hdl.handle.net/2381/30178.
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This thesis deals with sampled-data implementations of continuous-time, non-linear control systems. The basis for the analysis is a static, continuous-time feedback law for non-linear, affine systems with bounded input gain. The sampled-data implementation is obtained from the discretization of the control via a sample-and-hold-process. With the incorporation of the aspect of robustness, a theoretical framework is created which supersedes previous work concentrating on stability. Bounding constraints for the closed-loop differential system allow uncertainty and disturbances to be considered. Other assumptions for the continuous-time control are Lipschitz continuity, exponential decay outside a compact set and existence of a Lyapunov function. The important parameter for the discretization analysis is the sampling time; fast sampling implies robust stability. The controller sampling residual, the difference between the discretized and the original control, is of key interest within a Lyapunov-type stability analysis; suitable norms, such as the Euler norm, are chosen to find upper bounds for the sampling residual. The generalization of a result from linear to non-linear sampled-data control permits the application of the Lp-norm. The theoretical framework is also suitable for dynamic control systems and the investigation of computational delays. The analysis approaches are demonstrated for two different robust control. strategies .based on sliding-mode approaches. A state-feedback sliding-mode-based control extends ideas for smoothing discontinuous sliding-mode control components by introducing a cone-shaped sliding-mode layer. A non-smooth Lyapunov function is used to prove stability of the discretized control. An observer-based tracking control improves a previous control scheme by considering a class of non-minimum phase and relative-degree-zero plants. Simulation and numerical fast-sampling analysis results are provided for all developed discretization and sliding-mode-based control techniques in application to non-trivial examples. The simulation of a highly non-linear, large-scale chemical plant for benzene production with non-minimum phase and relative-degree-zero characteristics proves the effectiveness of sliding-mode output control.
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Scibile, Luigi. "Non-linear control of the plasma vertical position in a tokamak". Thesis, University of Oxford, 1997. http://ora.ox.ac.uk/objects/uuid:e64ad4bf-bd05-448f-8ac7-6d81aa8a65cb.
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The thesis describes the design of a novel non-linear controller for the plasma vertical position in a Tokamak that maximizes the stability region and is robust to certain disturbances and measurement noise. The plasma vertical position in a Tokamak can be open loop unstable with time-varying dynamics. The limitation in the output power of the control amplifier makes the time varying unstable system particularly difficult to control. Fixed-coefficient linear controllers usually fail to maintain control in the presence of large disturbances, like Edge Localized Modes (ELMs), which saturate the amplifier output. During the saturation period the vertical position of the plasma will grow exponentially with the unstable eigenvalue and may reach values that cannot be controlled by the energy provided by the control amplifier which is limited by economic restraints. The primary sources of disturbances and measurement noise that effect the vertical position are the ELMs and the 600Hz noise from the thyristor power supplies. The former are present during high energy confinement plasma configurations in the form pulses. A simple model structure is derived for the vertical position which includes the effect of the disturbances and the measurement noise and the control amplifier. The model is validated against experimental data from the JET and the COMPASS-D Tokamaks. A method to measure the maximum obtainable stability region of unstable systems subject to control limitations is derived and used to determine the conditions for a maximum stabilizer controller. A novel technique to determine the existence, the stability and the period of possible limit cycles for relay controlled systems is derived and used to determine the stability region of unstable systems incorporating relay controllers with and without time delays. A novel non-linear controller for the vertical position based on a discrete time adaptive near-minimum time algorithm (DANTOC) is designed to stabilize the system, to maximize the stability region and to be robust to the aforementioned sources of disturbances and measurement noise. The controller is tested in simulation for the JET Tokamak and the results demonstrate its feasibility in controlling the vertical position for different plasma configurations. The controller is also tested on the COMPASS-D Tokamak and the results demonstrate the improvement with respect to a simple linear P + D controller in the presence of the aforementioned sources of disturbances and measurement noise. The proposed controller represents a much better solution than existing conventional controllers for the control of the plasma vertical position for the new generation of Tokamaks.
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Liu, Jui-jung. "The practical identification on non-linear systems in the time and frequency domain". Thesis, University of Sheffield, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387761.
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Tu, Zhiqi. "Enhancements of the Non-linear Knapsack Cryptosystem". Thesis, University of Canterbury. Computer Science and Software Engineering, 2006. http://hdl.handle.net/10092/1080.
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Nowadays all existing public key cryptosystems are classified into three categories relied on different mathematical foundations. The first one is based on the difficulty of factoring the product of two big prime numbers. The representatives are the RSA and the Rabin cryptosystems. The second one such as the ElGamal cryptosystem is based on the discrete logarithm problem. The last one is based on the NP-completeness of the knapsack problem. The first two categories survived crypto attacks, whereas the last one was broken and there has been no attempt to use such a cryptosystem. In order to save the last category, Kiriyama proposed a new public key cryptosystem based on the non-linear knapsack problem, which is an NP-complete problem. Due to the non-linear property of the non-linear knapsack problem, this system resists all known attacks to the linear knapsack problem. Based on his work, we extend our research in several ways. Firstly, we propose an encrypted secret sharing scheme. We improve the security of shares by our method over other existing secret sharing schemes. Simply speaking, in our scheme, it would be hard for outsiders to recover a secret even if somehow they could collect all shares, because each share is already encrypted when it is generated. Moreover, our scheme is efficient. Then we propose a multiple identities authentication scheme, developed on the basis of the non-linear knapsack scheme. It verifies the ownership of an entity's several identities in only one execution of our scheme. More importantly, it protects the privacy of the entities from outsiders. Furthermore, it can be used in resource-constrained devices due to low computational complexity. We implement the above schemes in the C language under the Linux system. The experimental results show the high efficiency of our schemes, due to low computational complexity of the non-linear knapsack problem, which works as the mathematical foundation of our research.
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Swensen, Ingrid. "Modeling and Non-linear Control of Gel Breaking in Drilling Operations". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for teknisk kybernetikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-25754.
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As the petrolium operators are drilling deeper and more complicated well paths, extreme downhole presure variations during drilling operations may cause damage to equipment. This may in addition result in production restrictions and increased cost. Therefore, the main purpose of this project was to develop a non-linear control structure to stabilize the downhole pressure, such that the pressure never exceeds the $\pm$ 2 bar limit when the mud pump was started. Mud pump startup is one of the main reasons for increased pressure. Mud at rest will, after some time, start the process of gelling. When the system is set to motion again, a considerable amount of force is therefore required to break the gel. In order to achieve pressure stabilization, a controller was implemented on the mud pump. This controller included two proportional controllers, one monitored the downhole pressure, while the other used the calculated structure of the mud as an input parameter, meaning that the gelling was taken into account. The effects from a controlled back pressure pump were also assessed. Incorporating automatic contol on the mud pump resulted in a downhole pressure that remained within the $\pm$ 2 bar boundaries. The pump was able to provide the desired flow rate in a reasonable amount of time. This is because the pump decreased the flow only when the downhole pressure increased at an excessive rate, giving the gelled mud more time to brake.Throughout the project, the back pressure pump was implemented as a constant flow rate. A test scenario where the back pressure pump was a subject of automatic control showed a slight improvement with regards to downhole pressure stabilization, as well as a more stable choke valve opening. Automatic back pressure control might result in improved startup and shutdown timing. With two controllers, one on the choke valve and one on the mud pump, a more stable mud break-down process can be achieved. This can lead to several economic advantages such as time saved when returning to reference flow rate, less wear on the choke valve, as well as fewer operators needed to handle the mud pump.
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Kong, Kou A. "Fuzzy logic PD control of a non-linear inverted flexible pendulum". [Chico, Calif. : California State University, Chico], 2009. http://hdl.handle.net/10211.4/90.
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Basna, Rani. "Mean Field Games for Jump Non-Linear Markov Process". Doctoral thesis, Linnéuniversitetet, Institutionen för matematik (MA), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-55852.
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The mean-field game theory is the study of strategic decision making in very large populations of weakly interacting individuals. Mean-field games have been an active area of research in the last decade due to its increased significance in many scientific fields. The foundations of mean-field theory go back to the theory of statistical and quantum physics. One may describe mean-field games as a type of stochastic differential game for which the interaction between the players is of mean-field type, i.e the players are coupled via their empirical measure. It was proposed by Larsy and Lions and independently by Huang, Malhame, and Caines. Since then, the mean-field games have become a rapidly growing area of research and has been studied by many researchers. However, most of these studies were dedicated to diffusion-type games. The main purpose of this thesis is to extend the theory of mean-field games to jump case in both discrete and continuous state space. Jump processes are a very important tool in many areas of applications. Specifically, when modeling abrupt events appearing in real life. For instance, financial modeling (option pricing and risk management), networks (electricity and Banks) and statistics (for modeling and analyzing spatial data). The thesis consists of two papers and one technical report which will be submitted soon: In the first publication, we study the mean-field game in a finite state space where the dynamics of the indistinguishable agents is governed by a controlled continuous time Markov chain. We have studied the control problem for a representative agent in the linear quadratic setting. A dynamic programming approach has been used to drive the Hamilton Jacobi Bellman equation, consequently, the optimal strategy has been achieved. The main result is to show that the individual optimal strategies for the mean-field game system represent 1/N-Nash equilibrium for the approximating system of N agents. As a second article, we generalize the previous results to agents driven by a non-linear pure jump Markov processes in Euclidean space. Mathematically, this means working with linear operators in Banach spaces adapted to the integro-differential operators of jump type and with non-linear partial differential equations instead of working with linear transformations in Euclidean spaces as in the first work. As a by-product, a generalization for the Koopman operator has been presented. In this setting, we studied the control problem in a more general sense, i.e. the cost function is not necessarily of linear quadratic form. We showed that the resulting unique optimal control is of Lipschitz type. Furthermore, a fixed point argument is presented in order to construct the approximate Nash Equilibrium. In addition, we show that the rate of convergence will be of special order as a result of utilizing a non-linear pure jump Markov process. In a third paper, we develop our approach to treat a more realistic case from a modelling perspective. In this step, we assume that all players are subject to an additional common noise of Brownian type. We especially study the well-posedness and the regularity for a jump version of the stochastic kinetic equation. Finally, we show that the solution of the master equation, which is a type of second order partial differential equation in the space of probability measures, provides an approximate Nash Equilibrium. This paper, unfortunately, has not been completely finished and it is still in preprint form. Hence, we have decided not to enclose it in the thesis. However, an outlook about the paper will be included.
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O'Dea, Enda. "Robust control of non-linear 2D and linear 3D disturbances in channel flow by surface transpiration". Thesis, University of Southampton, 2004. https://eprints.soton.ac.uk/47092/.
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The attenuation of perturbations in both periodic and non-periodic channel flow is attempted through wall-normal transcription and point wall-shear-stress measurements. The transcription is applied in both continuous harmonic form and a system based on discrete zero-net-mass-flux panel-pair form. For 2D flow it is demonstrated by means of a spectral Galerkin solver, that a simple classical controller with harmonic transpiration is capable of attenuating highly non-linear 2D perturbations. A multiple-input/multiple-output (MIMO) robust control scheme designed for the attenuation of perturbations in a non-periodic channel is applied to linear perturbations in the periodic setting. A certain set of linearly unstable modes in this periodic setting prove unstable for this control scheme. The significance of the last panel-pair in the scheme's failure in the presence of such modes is also demonstrated to continue to attenuate simple 2D perturbations in the presence of certain prescribed actuator/sensor faults. The identification of which faults are detrimental to the control demonstrates the importance of upstream actuators and downstream sensors respectively. Such observations may be useful in the design of fault tolerant control schemes. An ad-hoc extension of the 2D MIMO controller is applied to a 3D flow. A simple perturbation is initialised in the flow by an upstream panel pair
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Chia, Andy. "Explorations in Quantum Measurement and Control". Thesis, Griffith University, 2011. http://hdl.handle.net/10072/366552.
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This thesis presents the theory of LQG (linear-quadratic-Gaussian) and Markovian feedback
control for quantum systems.
We devote Part I to a review of both classical and quantum feedback but with an emphasis
on LQG and linear systems control. The language of classical stochastic control is that
of probability theory and stochastic differential equations. Thus we first introduce the
essential mathematics (within the context of measurement and control) such as the Kushner–
Stratonovich and Langevin equations. We then specialize to linear classical systems and
introduce traditional engineering principles such as stabilizing solutions of Riccati equations,
controllability, certainty equivalence, and the like. The classical Kushner–Stratonovich and
Langevin equations have well-known quantum analogues — the stochastic master equation
and the quantum Langevin equation. These, and other relevant tools for doing quantum
feedback control are reviewed. Subsequently the concepts of stabilizing solutions of Riccati
equations, controllability, separation theorem, amongst other related notions are shown to
be adaptable for quantum systems. An essential difference between quantum and classical
feedback lies in the in-loop measurement. Quantum measurements induce quantum backaction,
non-existent in classsical measurements. This means the measurement strength and
strategy in a quantum feedback loop should be optimized for a given control objective. We
illustrate each of these points with examples in LQG control.
Part II is devoted to the theory of diffusive quantum measurements (measurements that
have Gaussian distributed outcomes) and Markovian feedback control for nonlinear systems.
A new and general representation of diffusive quantum measurements is derived. This
representation is compared with an old representation (which we introduce in Part I) and
shown to possess advantages over the old representation. We also propose a quantum optical
scheme as a universal method for physically realizing diffusive quantum measurements. Our
new representation of diffusive measurements is then applied to build a general theory of
multiple-input multiple-output Markovian quantum feedback. Previously known results of
Markovian feedback are reproduced as special cases of this more general framework.This work has not previously been submitted for a degree or diploma in any university.
To the best of my knowledge and belief, the thesis contains no material previously published
or written by another person except where due reference is made in the thesis itself.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Science, Environment, Engineering and Technology
Full Text
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Pedchote, C. "Parameter estimation for non-linear systems: an application to vehicle dynamics". Thesis, Engineering Systems Department, 2009. http://hdl.handle.net/1826/3896.
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This work presents an investigation into the parameter estimation of suspension
components and the vertical motions of wheeled vehicles from experimental data. The
estimation problems considered were for suspension dampers, a single wheel station and
a full vehicle.
Using conventional methods (gradient-based (GB), Downhill Simplex (DS)) and
stochastic methods (Genetic Algorithm (GA) and Differential Evolution (DE)), three
major problems were encountered. These were concerned with the ability and consistency
of finding the global optimum solution, time consumption in the estimation process, and
the difficulties in setting the algorithm's control parameters. To overcome these
problems, a new technique named the discrete variable Hybrid Differential Evolution
(dvHDE) method is presented.
The new dvHDE method employs an integer-encoding technique and treats all
parameters involved in the same unified way as discrete variables, and embeds two
mechanisms that can be used to deal with convergence difficulties and reduce the time
consumed in the optimisation process. The dvHDE algorithm has been validated against
the conventional GB, DS and DE techniques and was shown to be more efficient and
effective in all but the simplest cases. Its robustness was demonstrated by its application
to a number of vehicle related problems of increasing complexity. These include case
studies involving parameter estimation using experimental data from tests on automotive
dampers, a single wheel station and a full vehicle. The investigation has shown that the
proposed dvHDE method, when compared to the other methods, was the best for finding
the global optimum solutions in a short time. It is recommended for nonlinear vehicle
suspension models and other similar systems.
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Pedchote, Chamnarn. "Parameter estimation for non-linear systems : an application to vehicle dynamics". Thesis, Cranfield University, 2003. http://dspace.lib.cranfield.ac.uk/handle/1826/3896.
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This work presents an investigation into the parameter estimation of suspension components and the vertical motions of wheeled vehicles from experimental data. The estimation problems considered were for suspension dampers, a single wheel station and a full vehicle. Using conventional methods (gradient-based (GB), Downhill Simplex (DS)) and stochastic methods (Genetic Algorithm (GA) and Differential Evolution (DE)), three major problems were encountered. These were concerned with the ability and consistency of finding the global optimum solution, time consumption in the estimation process, and the difficulties in setting the algorithm's control parameters. To overcome these problems, a new technique named the discrete variable Hybrid Differential Evolution (dvHDE) method is presented. The new dvHDE method employs an integer-encoding technique and treats all parameters involved in the same unified way as discrete variables, and embeds two mechanisms that can be used to deal with convergence difficulties and reduce the time consumed in the optimisation process. The dvHDE algorithm has been validated against the conventional GB, DS and DE techniques and was shown to be more efficient and effective in all but the simplest cases. Its robustness was demonstrated by its application to a number of vehicle related problems of increasing complexity. These include case studies involving parameter estimation using experimental data from tests on automotive dampers, a single wheel station and a full vehicle. The investigation has shown that the proposed dvHDE method, when compared to the other methods, was the best for finding the global optimum solutions in a short time. It is recommended for nonlinear vehicle suspension models and other similar systems.
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Thapa, Bal K. "Neural network enhanced self tuning adaptive control application for non-linear control of dynamic systems". Thesis, Aston University, 2001. http://publications.aston.ac.uk/11767/.
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The main theme of research of this project concerns the study of neutral networks to control uncertain and non-linear control systems. This involves the control of continuous time, discrete time, hybrid and stochastic systems with input, state or output constraints by ensuring good performances. A great part of this project is devoted to the opening of frontiers between several mathematical and engineering approaches in order to tackle complex but very common non-linear control problems. The objectives are: 1. Design and develop procedures for neutral network enhanced self-tuning adaptive non-linear control systems; 2. To design, as a general procedure, neural network generalised minimum variance self-tuning controller for non-linear dynamic plants (Integration of neural network mapping with generalised minimum variance self-tuning controller strategies); 3. To develop a software package to evaluate control system performances using Matlab, Simulink and Neural Network toolbox. An adaptive control algorithm utilising a recurrent network as a model of a partial unknown non-linear plant with unmeasurable state is proposed. Appropriately, it appears that structured recurrent neural networks can provide conveniently parameterised dynamic models for many non-linear systems for use in adaptive control. Properties of static neural networks, which enabled successful design of stable adaptive control in the state feedback case, are also identified. A survey of the existing results is presented which puts them in a systematic framework showing their relation to classical self-tuning adaptive control application of neural control to a SISO/MIMO control. Simulation results demonstrate that the self-tuning design methods may be practically applicable to a reasonably large class of unknown linear and non-linear dynamic control systems.
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Ghwanmeh, Sameh Hussein. "The investigation of on-line self-learning fuzzy logic control for non-linear processes". Thesis, Liverpool John Moores University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337808.
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Hong, Xia. "Non-linear time series modelling and prediction with radial basis function network based algorithms". Thesis, University of Sheffield, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286888.
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Sridhar, Siddharth. "Non-Linear Control of a Tilt-Rotor Quadcopter using Sliding Mode Technique". University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1592170442729443.
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Leppäkoski, K. (Kimmo). "Utilisation of non-linear modelling methods in flue-gas oxygen-content control". Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514282418.
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Abstract
Non-linear methods have been utilised in modelling the processes on a flue-gas oxygen-content control system of a power plant. The ultimate objective is to reduce NOx and CO emissions by enhancing the control system. By investigating the flue-gas emission control strategy, the major factors affecting the flue-gas emissions have been determined. A simulator has been constructed, and it emulates a real process automation system and its physical processes. The process models of the simulator are: a flue-gas oxygen-content model, a secondary air flow model, a primary air flow model and a fuel feeding screw model (a fuel flow). The effort has been focused on two plant models: the flue-gas oxygen-content model and the secondary air flow model. Combustion is a non-linear, timevariant, multi-variable process with a variable delay. The secondary air model is a non-linear, timeinvariant (in principle), multi-variable system. Both phenomenological modelling (mass and energy calculations) and black-box modelling (neural networks) have been utilised in the Wiener/Hammerstein structures. It is possible to use a priori knowledge in model modifying, and therefore the model of flue-gas oxygen-content can be tuned on site. The simulator with precalculated parameters was tested in a full-scale power plant and a pilot-scale circulating fluidised bed boiler. The results in the power plant were remarkable since NOx emissions decreased significantly without increasing CO emissions.