Instead of dissipating vibration energy into heat waste via viscous damping elements, this dissertation proposes an innovative vibration control method which can simultaneously mitigate vibration and harvest the associated vibration energy using electromagnetic energy harvesters. This dissertation shows that the electromagnetic energy harvester can work as a controllable damper as well as an energy harvester. The semi-active control of a linear electromagnetic energy harvester, for improvement of suspension performance, has been experimentally implemented in a scaled-down quarter-car suspension system. While improving performance, power produced by the harvester can be harvested through energy harvesting circuits. This dissertation also proposes a mechanical-motion-rectifier(MMR)-based electromagnetic energy harvester using a ball-screw mechanism and two one-way clutches for the application of replacing the viscous damper in vehicle suspensions. Compared to commercial linear harvesters, the proposed design is able to provide large damping forces and increase power-dissipation density, making it suitable to vehicle suspensions. In addition, the proposed MMR-based harvester can convert reciprocating vibration into unidirectional rotation of the generator. This feature significantly increases energy-harvesting efficiency by enabling the generator to rotate at a relatively steady speed during irregular vibrations and improves the system reliability by reducing impact forces among transmission gears. Extensive theoretical and experimental analysis have been conducted to characterize the proposed MMR-based energy harvester. The coupled dynamics of the suspension system with the MMR-based energy harvester are also explored and optimized. Furthermore, a new control algorithm is proposed to control the MMR-based energy harvester considering its unique dynamics induced by the one-way clutches. The results show that the controlled proposed electromagnetic energy harvester can possibly improve ride comfort of vehicles over conventional oil dampers and simultaneously harvest the associated vibration energy. / Ph. D.

Hunting is a very common instability exhibited by rail vehicles operating at high speeds. The hunting phenomenon is a self excited lateral oscillation that is produced by the forward speed of the vehicle and the wheel-rail interactive forces that result from the conicity of the wheel-rail contours and the friction-creep characteristics of the wheel-rail contact geometry. Hunting can lead to severe ride discomfort and eventual physical damage to wheels and rails. A comprehensive study of the lateral stability of a single wheelset, a single truck, and the complete rail vehicle has been performed. This study investigates bifurcation phenomenon and limit cycles in rail vehicle dynamics. Sensitivity of the critical hunting velocity to various primary and secondary stiffness and damping parameters has been examined. This research assumes the rail vehicle to be moving on a smooth, level, and tangential track, and all parts of the rail vehicle to be rigid. Sources of nonlinearities in the rail vehicle model are the nonlinear wheel-rail profile, the friction-creep characteristics of the wheel-rail contact geometry, and the nonlinear vehicle suspension characteristics. This work takes both single-point and two-point wheel-rail contact conditions into account. The results of the lateral stability study indicate that the critical velocity of the rail vehicle is most sensitive to the primary longitudinal stiffness. A method has been developed to eliminate hunting behavior in rail vehicles by increasing the critical velocity of hunting beyond the operational speed range. This method involves the semi-active control of the primary longitudinal stiffness using the wheelset yaw displacement. This approach is seen to considerably increase the critical hunting velocity. / Master of Science

L'amélioration permanente de la qualité et des performances des systèmes automatiques constitue un défi majeur dans la théorie du contrôle. La théorieHinf a permis d'améliorer considérablement les performances des correcteurs. Ces derniers reposent sur des modèles mathématiques qui sont potentiellement d'ordre élevé (c.-à-d. comprenant un nombre élevé d'équations différentielles). De plus, l'ajout de poids de pondérations spécifiant les performances à respecter accroit encore plus leur ordre. La complexité algorithmique résultante peut alors rendre leur implantation difficile voire même impossible pour un fonctionnement en temps réel.Les travaux présentés visent à réduire l'ordre de correcteurs Hinf dans le but de faciliter leur intégration tout en respectant les performances imposées d'une part et proposent une majoration de l'erreur introduite par l'étape de réduction d'autre part.Dans la littérature, de nombreuses méthodes pour la réduction d'ordre de modèles et de correcteurs des systèmes LTI ont été développées. Ces techniques ont été étudiées, comparées et testées sur un ensemble de benchmarks. S'appuyant sur ces travaux, nous proposons une extension aux systèmes linéaires à paramètres variants (LPV). Pour valider leurs performances, une application sur une commande d'une suspension semi-active a montré l'efficacité des algorithmes de réduction développés. / The work presented in this dissertation is related to the Hinf-LPV-controller orderReduction. This latter consists of the design of a robust reduced-order LPV-controller for LPV-systems. The order reduction issue has been very fairly investigated. However, the case of LPV-control design is slightly discussed. This thesis focuses primarily on two topics: How to obtain an LPV-reduced-order controller even the high order generated by the classical synthesis and how this reduced order controller can deal with a practical engineering problem (semi-active suspension control). In view of this, the order-reduction topic and the Hinf-synthesis theory have been widely studied in this thesis. This study, has allowed the development of a new method forH1-LPV-controller order reduction.