In the field of mobile robotics, many applications require feedback control laws that provide perfect path following. Previous work has shown that transverse feedback linearization is an effective approach to designing path following controllers that achieve perfect path following and path invariance. This thesis uses transverse feedback linearization and augments it with dynamic extension to present a framework for designing path following controllers for certain kinematic models of mobile robots. This approach can be used to design path following controllers for a large class of paths. While transverse feedback linearization makes the desired path attractive and invariant, dynamic extension allows the closed-loop system to achieve the desired motion along the path. In particular, dynamic extension can be used to make the mobile robot track a desired velocity or acceleration profile while moving along a path.

The global greenhouse gas CO2 emission from the transportation sector is very significant. To reduce this gas emission, EU has set an average target of not more than 95 CO2/km for new passenger cars by the year 2020. A great reduction is still required to achieve the CO2 emission target in 2020, and many different approaches are being considered. This thesis focuses on the thermal management of the engine as an area that promise significant improvement of fuel efficiency with relatively small changes. The review of the literature shows that thermal management can improve engine efficiency through the friction reduction, improved air-fuel mixing, reduced heat loss, increased engine volumetric efficiency, suppressed knock, reduce radiator fan speed and reduction of other toxic emissions such as CO, HC and NOx. Like heat loss and friction, most emissions can be reduced in high temperature condition, but this may lead to poor volumetric efficiency and make the engine more prone to knock. The temperature trade-off study is conducted in simulation using a GT-SUITE engine model coupled with the FE in-cylinder wall structure and cooling system. The result is a map of the best operating temperature over engine speed and load. To quantify the benefit of this map, eight driving styles from the legislative and research test cycles are being compared using an immediate application of the optimal temperature, and significant improvements are found for urban style driving, while operation at higher load (motorway style driving) shows only small efficiency gains. The fuel consumption saving predicted in the urban style of driving is more than 4%. This assess the chance of following the temperature set point over a cycle, the temperature reference is analysed for all eight types of drive cycles using autocorrelation, lag plot and power spectral density. The analysis consistently shows that the highest volatility is recorded in the Artemis Urban Drive Cycle: the autocorrelation disappears after only 5.4 seconds, while the power spectral density shows a drop off around 0.09Hz. This means fast control action is required to implement the optimal temperature before it changes again. Model Predictive Control (MPC) is an optimal controller with a receding horizon, and it is well known for its ability to handle multivariable control problems for linear systems with input and state limits. The MPC controller can anticipate future events and can take control actions accordingly, especially if disturbances are known in advance. The main difficulty when applying MPC to thermal management is the non-linearity caused by changes in flow rate. Manipulating both the water pump and valve improves the control authority, but it also amplifies the nonlinearity of the system. Common linearization approaches like Jacobian Linearization around one or several operating points are tested, by found to be only moderately successful. Instead, a novel approach is pursued using feedback linearization of the plant model. This uses an algebraic transformation of the plant inputs to turn the nonlinear systems dynamics into a fully or predominantly linear system. The MPC controller can work with the linear model, while the actual control inputs are found using an inverse transformation. The Feedback Linearization MPC of the cooling system model is implemented and testing using MathWork Simulink®. The process includes the model transformation approach, model fitting, the transformation of the constraints and the tuning of the MPC controller. The simulation shows good temperature tracking performance, and this demonstrates that a MPC controller with feedback linearization is a suitable approach to thermal management. The controller strategy is then validated in a test rig replicating an actual engine cooling system. The new MPC controller is again evaluated over the eight driving cycles. The average water pump speed is reduced by 9.1% compared to the conventional cooling system, while maintaining good temperature tracking. The controller performance further improves with future disturbance anticipation by 20.5% for the temperature tracking (calculated by RMSE), 6.8% reduction of the average water pump speed, 47.3% reduction of the average valve movement and 34.0% reduction of the average radiator fan speed.

As válvulas de controle são elementos finais muito importantes na indústria de processos, pois são as responsáveis por controlar a pressão em dutos ou vazão dos fluidos de processo, impactando diretamente na qualidade do produto final. Por serem elementos mecânicos móveis estão sujeitas ao atrito, uma não linearidade que quando excessiva, pode causar oscilações e erros na abertura da válvula. A presença de oscilações nas malhas de controle aumenta a variabilidade das variáveis de processo, o desgaste dos componentes e o consumo de energia, além de provocar o desperdício de materiais. O desenvolvimento de novas técnicas de compensação de atrito é fundamental para melhorar o desempenho das malhas de controle, sendo, portanto, de grande interesse para a indústria de processos industriais. Este trabalho apresenta o estudo de cinco compensadores não lineares: controlador rastreador de trajetória, controlador por modos deslizantes, controlador por modos deslizantes integrador, controlador por modelo interno não linear e controlador PI não linear, os quais são desenvolvidos desde a teoria à implementação prática em uma válvula de controle real. Os resultados obtidos, mostram que os controladores projetados apresentaram desempenho bastante satisfatórios, sendo que o controlador por modos deslizantes e por modos deslizante integrador apresentaram os melhores desempenho. / Control valves are very important final elements in process industry, due they are the responsible to control the pressure in pipelines and the flow of the process fluids, directly impacting in the quality of the final product. Due to the mechanical mobile elements, they are subjected to friction, a nonlinearity that can generate oscillations and errors in the valve aperture. Oscillations in the control loops increase the process variability, wear in the actuators and the power consumption, besides generating raw material waste. The development of new friction compensation techniques is very important to increase the control loops performance, therefore, it is of great interest for the process industry. This work presents the study of five nonlinear compensators: Trajectory tracking controller, sliding mode controller, sliding mode controller integrator, nonlinear internal model controller and nonlinear PI controller, which ones are developed from theory to practical implementation in a real control valve. The results show that the controllers presented satisfactory performance, where the sliding mode controller and sliding mode control integrator presented the best performance.

Táto diplomová práca sa zaoberá návrhom a konštrukciou elektromagnetickej, polohovacej platformy, pre testovanie nelineárnych riadiacich a identifikačných algoritmov. Platforma je založená na tvarovaní magnetického poľa v každom bode pomocou troch elektromagnetov a polohuje oceľovú guličku po dotykovom paneli ktorý sníma polohu tejto guličky. Platforma má slúžiť hlavne pre demonštráciu rôznych nelineárnych riadiacich algoritmov vo výukovom prostredí. Tri príklady takýchto algoritmov sú ukázané a overené v rámci tejto diplomovej práce.

Cette thèse étudie l'approche LPV pour la commande robuste des systèmes non linéaires. Son originalité est de proposer pour la première fois un cadre rigoureux permettant de résoudre efficacement des problèmes de synthèse non linéaire. L'approche LPV a été proposée comme une extension de l'approche H-infini dans le contexte des systèmes LPV (« Linéaires à Paramètres Variant dans le temps »), voire non linéaires. Quoique prometteuse, cette approche pour la commande des systèmes non linéaires restait peu utilisée. En effet, au-delà même de certaines limitations théoriques, la nature des solutions obtenues semblait inadéquate. Cette question ouverte est notre point de départ. Nous montrons tout d'abord que la faible variation des correcteurs constatée est due avant tout à la nature du schéma informationnel utilisé traditionnellement lors de la synthèse LPV, et que sous des hypothèses raisonnables, le cadre LPV peut permettre de recouvrir des stratégies de type « linéarisation par bouclage ». Ce point étant acquis, une deuxième difficulté réside dans l'obtention effective de correcteurs non linéaires donnant des garanties de performance. Nous proposons un cadre rigoureux permettant de résoudre efficacement un problème de synthèse incrémentale pondérée, par la résolution d'un problème LPV associé à un schéma informationnel spécifique compatible avec celui identifié dans la première partie. Cette étude et son aboutissement à la définition d'un cadre formel et d'une procédure complète d'obtention de correcteurs, incluant des méthodes de réduction de complexité, donnent des arguments puissants en faveur de l'approche LPV pour la commande robuste de systèmes non linéaires. / This thesis studies the LPV approach for the robust control of nonlinear systems. Its originality is to propose for the first time a rigorous framework allowing to solve efficiently nonlinear synthesis problems.The LPV approach was proposed as an extension of the H-infinity approach in the context of LPV (Linear Parameter-Varying) systems and nonlinear systems. Although this approach seemed promising, it was not much used in practise. Indeed, beyond certain theoretical limitations, the nature itself of the obtained solutions did not seem adequate. This open question constitutes the starting point of our work.We first prove that the observed weak variation of the controllers is in fact mostly due to the information structure traditionally used for LPV synthesis, and that under reasonable assumptions, the LPV framework can overlap feedback linearization strategies. This point having been resolved, a second difficulty lies in the actual achievement of nonlinear controllers yielding performance guarantees. We propose a rigorous framework allowing to solve efficiently an incremental synthesis problem, through the resolution of an LPV problem associated to a specific information structure compatible with the one identified in the first part.This study and its corollary description of a formal framework and of a complete controller synthesis procedure, including complexity reduction methods, provide powerful arguments in favor of the LPV approach for the robust control of nonlinear systems.

In this thesis, dynamic modeling and nonlinear control of autonomous underwater vehicle manipulator systems are presented. Mainly, two types of systems consisting of a 6-DOF AUV equipped with a 6-DOF manipulator subsystem (UVMS) and with an 8-DOF redundant manipulator subsystem (UVRMS) are modeled considering hydrostatic forces and hydrodynamic effects such as added mass, lift, drag and side forces. The shadowing effects of the bodies on each other are introduced when computing the hydrodynamic forces. The system equations of motion are derived recursively using Newton&ndash / Euler formulation. The inverse dynamics control algorithms are formulated and trajectory tracking control of the systems is achieved by assigning separate tasks for the end effector of the manipulator and for the underwater vehicle. The proposed inverse dynamics controller utilizes the full nonlinear model of the system and consists of a linearizing control law that uses the feedback of positions and velocities of the joints and the underwater vehicle in order to cancel off the nonlinearities of the system. The PD control is applied after this complicated feedback linearization process yielding second order error dynamics. The thruster dynamics is also incorporated into the control system design. The stability analysis is performed in the presence of parametric uncertainty and disturbing ocean current. The effectiveness of the control methods are demonstrated by simulations for typical underwater missions.

In this thesis, dynamic modeling and nonlinear control of autonomous underwater vehicle manipulator systems are presented. Mainly, two types of systems consisting of a 6-DOF AUV equipped with a 6-DOF manipulator subsystem (UVMS) and with an 8-DOF redundant manipulator subsystem (UVRMS) are modeled considering hydrostatic forces and hydrodynamic effects such as added mass, lift, drag and side forces. The shadowing effects of the bodies on each other are introduced when computing the hydrodynamic forces. The system equations of motion are derived recursively using Newton&ndash / Euler formulation. The inverse dynamics control algorithms are formulated and trajectory tracking control of the systems is achieved by assigning separate tasks for the end effector of the manipulator and for the underwater vehicle. The proposed inverse dynamics controller utilizes the full nonlinear model of the system and consists of a linearizing control law that uses the feedback of positions and velocities of the joints and the underwater vehicle in order to cancel off the nonlinearities of the system. The PD control is applied after this complicated feedback linearization process yielding second order error dynamics. The thruster dynamics is also incorporated into the control system design. The stability analysis is performed in the presence of parametric uncertainty and disturbing ocean current. The effectiveness of the control methods are demonstrated by simulations for typical underwater missions.

In recent years, there has been a significant increase in the interest for snake like modular robots due to their superior locomotion capabilities in terms of versatility, adaptability and scalability. Passive wheeled planar snake like robots are a major category and they are being actively researched. Due to the nonholonomic constraints imposed on them, certain configurations lead to the singularity which must be avoided at all costs. Furthermore, it is vital to generate a locomotion pattern such that they can track a wide range of trajectories. All of these objectives must be accomplished smoothly and in an energy efficient manner. Studies indicate that meeting all of these requirements is a challenging problem. In this study, a novel form of the serpenoid curve is proposed in order to make the robot track arbitrary paths. A controller has been designed using the feedback linearization method. Afterwards, a new performance measure, considering both the efficiency and sustainability of the locomotion, has been proposed to evaluate the locomotion. Optimal parameters for the proposed serpenoid curve and the linear controller have been determined for efficient locomotion by running series of simulations. Relations between the locomotion performance, locomotion speed and eigenvalues of the linear controller have been demonstrated. Simulation results show striking differences between the locomotion by using the proposed serpenoid curve with optimal parameters and the locomotion by purely tracking a given path. Obtained results also indicate that the aforementioned requirements are met successfully and confirm the validity and consistency of the proposed performance measure.

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Direct drive wave energy conversion systems have been identified as a potentially major contributor to the world’s energy demands, forecasting shares of up to 25 % of the energy mix. Anders Hagnestål conducts research at the Royal Institute of Technology where a novel linear transverse flux permanent magnet generator is developed. This concept machine is particularly well-suited for the pertaining operating conditions in marine environments, producing large forces at low speeds with outstandingly low resistive losses. However, it exhibits severe magnetic saturation and draws unsymmetrical phase currents at nominal operation. In addition, it possesses a low power factor. All in all, this places stern requirements on the power electronic system and control algorithms. The aim of this thesis has been to design a functioning power conditioning system that connects the machine to the electric grid. For this purpose, a three-phase two-level voltage source converter is proposed to be back-to-back connected with two-level single-phase voltage source converters (active rectifiers) interfacing each and every machine phase. It is shown that the intermediate DC link can be maintained at a constant voltage with restricted ripple while feeding power at unity power factor to the grid by appropriately sizing the DC capacitor and adopting a feedback linearization control scheme. The phase currents can be controlled effectively by means of a cascaded gain-scheduled PID controller. By including a low-pass filter the iron losses in the machine may be suppressed even at lower switching frequencies. A constrained cost optimization indicates that the converter consequently can reach 99.1 % efficiency. Finally, with this thesis as a background, it is suggested that the thermal stresses on the selected semiconductor modules and the iron losses of the machine are evaluated to further improve the design. If higher efficiency of the active rectifiers is strived for, more complex converter topologies could be considered. / Direktdrivna vågenergiomvandlingssystem har utpekats som en potentiellt starkt bidragande resurs för att tillgodose världens efterfrågan på energi med andelar på uppemot 25 % av energimixen förutspådda. Anders Hagnestål bedriver forskning och utveckling av en ny typ av linjär permanentmagnetiserad transversalflödesmaskin vid Kungliga Tekniska Högskolan. Konceptmaskinen är särskilt väl lämpad för de rådande marina förhållandena genom att kunna producera stora krafter vid låga hastigheter med utomordentligt låga resistiva förluster. Maskinen går emellertid i kraftig magnetisk mättnad och drar asymmetriska strömmar vid nominell drift. Dessutom är effektfaktorn låg i jämförelse med standardmaskiner. Alltsomallt inför detta hårda krav på det effektelektroniska systemet och kontrollalgoritmerna. Målet med detta examensarbete har varit att designa ett funktionellt effektkonditioneringssystem som sammanfogar maskinen med det angränsande elektriska nätet. För att åstadkomma detta föreslås att en tvånivås-trefasomriktare kopplas rygg-mot-rygg till tvånivås-enfasomvandlare (aktiva likriktare) som i sin tur är kopplade till varje maskinfas. Med den här konfigurationen visas det att spänningen på den mellanliggande DC-länken kan hållas konstant med begränsat rippel, alltmedan effekt tillförs nätet vid effektfaktor ett genom att dimensionera DC-kondensatorn på rätt sätt och använda en kontrollag baserad på exakt linjärisering. Maskinens fasströmmar kan kontrolleras effektivt med hjälp av en kaskadkopplad PID-regulator med schemalagda förstärkningsfaktorer. Genom att inkludera ett lågpassfilter förväntas det att järnförlusterna i maskinen kan begränsas även vid lägre switchfrekvenser. Genom att lösa ett kostnadsoptimeringsproblem visas det att den resulterande aktiva likriktaren kan uppnå en verkningsgrad på 99.1 %. Slutligen, med det här examensarbetet som grund, föreslås det att den termiska stressen på de valda halvledarkomponentsmodulerna och järnförlusterna i maskinen utvärderas för att ytterligare förbättra designen. Om högre verkningsgrad eftersträvas hos de aktiva likriktarna kan mer komplicerade omvandlartopologier övervägas.