Induction machines are the most widely used type of electrical machines because of their robustness, simplicity, and relatively low cost. However, the small airgap in the induction machine makes them more susceptible to Unbalanced Magnetic Pull (UMP). This is because the magnitude of the UMP is a function of the degree of eccentricity, which is the ratio between the length of misalignment and the mean airgap length. The bearing-related failure accounts for approximately 41% of the total failures of induction machines; the percentages of bearing-related failure would be higher for applications in a harsher environment. In this thesis, the UMP caused by rotor eccentricity is investigated, because a small degree of rotor eccentricity is unavoidable due to the manufacturing tolerance and 80% of the mechanical faults could cause rotor eccentricity in electrical machines. When the rotor is not at the centre of the stator, the eccentric rotor causes an uneven airgap around the rotor, in which the magnetic permeance with the higher harmonics content will be created. The magnetomotive force (MMF) produces additional pole-pair ±1 magnetic flux around the airgap. The interaction between each magnetic flux with its pole pair ±1 magnetic flux produces UMP. As only the magnetic flux that crosses the airgap causes UMP, the magnetic flux is categorised into magnetising flux and airgap leakage flux, because both types of flux possess different characteristics at a different rotor slip. As the airgap leakage flux is difficult to calculate analytically, an empirical method is proposed to estimate the UMP caused by the airgap leakage flux. Then, the UMP caused by the magnetising flux can also be estimated by using the empirical method. The parameters for the empirical method can be found by using either the FEA or the experimental results. The damping effect of the magnetising flux in a parallel connected rotor bar is discussed and a damping coefficient is introduced to explain this scenario. The damping coefficient can also be used to calculate the UMP in a steady state analysis. UMP comparisons between the cage rotor and wound rotor induction machines are made. The wound rotor has a much higher UMP because the pole-specific wound rotor could not damp the additional pole pair ±1 magnetic flux. Therefore, a damper winding at the stator slot is also proposed in order to damp the UMP by producing a counteracting flux. In addition, analytical equations have also been derived for different scenarios, such as static eccentricity, dynamic eccentricity, axial-varying eccentricity, and skew rotor bars. Finite Element Analysis (FEA) and experimental work are used to demonstrate the derived analytical equation. Furthermore, the power losses caused by the rotor eccentricity are investigated. Iron losses, copper losses, and frictional loss are discussed and compared with both the analytical equation and the FEA results. In order to reduce the UMP in the induction machines, the two proposed methods are the slip control method and damper windings topology. The slip control method utilises the non-linearity characteristic of the UMP at different rotor slip. To find the optimum operating slip with the lowest UMP, the UMP/Torque ratio is introduced. The characteristics of the UMP/Torque ratio varies with the type and design of the induction machines. However, this method is only applicable when the machine is lightly loaded, because the magnetising flux is limited by the capped terminal voltage and the core saturation of the machine. For the damper winding topology, a circulating current flowing in the damper winding could produce a counteracting flux to damp the UMP. The proposed damper windings configuration is only suitable for the induction machine with an even pole pair number. Finally, comparisons between both UMP reduction methods are made.

As lesões de tornozelo, mais precisamente na articulação subtalar, chamadas de entorses, estão bastante presentes no âmbito esportivo. No futsal, esporte amplamente praticado em nosso país, a entorse por inversão do tornozelo está entre as lesões que mais acometem os atletas em todos os níveis de sua prática devido às exigências que o esporte impõe. Avaliações isocinéticas têm sido utilizadas na medição de performances musculares com o intuído de se obterem dados mais precisos em relação às forças produzidas por diferentes grupos musculares. A razão de torque e ativação são duas variáveis que podem ser medidas nestes testes servindo como parâmetro para detectar possíveis desequilíbrios musculares entre músculos agonistas/antagonistas. Este trabalho buscou avaliar as razões de torque e ativação, bem como a potência e o trabalho musculares realizados pela musculatura eversora e inversora do tornozelo em atletas de uma equipe de futsal. Foram avaliados 13 atletas, dos quais 7 atletas com lesão unilateral de tornozelo serviram de amostra para uma comparação entre o membro lesado e não lesado. As razões de torque e ativação da musculatura eversora e inversora do tornozelo foram avaliadas durante contrações isométricas voluntárias máximas nos ângulos de -20º de inversão, 0º e 20º de eversão, e isocinéticas concêntricas e excêntricas nas velocidades de 60º, 120º e 180º/s. As variáveis de trabalho e potência também foram obtidas nestes testes. As razões de torque foram obtidas com a divisão dos valores do pico de torque eversor pelo pico de torque inversor, e as razões de ativação da mesma forma, porém dividindo o valor RMS do sinal EMG dos músculos eversores Fibular Curto e Fibular Longo pelo músculo inversor Tibial Anterior. Os valores encontrados nas razões de torque convencionais e funcionais não demonstraram diferenças significativas entre o grupo de tornozelos com e sem lesão, com exceção da razão funcional inversora EVexc/INVcon, na qual foram encontrados valores maiores no grupo lesado, o que indica possível desequilíbrio na relação Ev/Inv. As razões de ativação não mostraram diferenças significativas entre os dois grupos. Já as variáveis trabalho e potência foram equivalentes nos dois grupos, o que demonstra que após a lesão e a recuperação destes atletas, e com a volta as atividades esportivas houve um reestabelecimento na produção das forças musculares que atuam na musculatura eversora e inversora do tornozelo. / The ankle injuries, more precisely in "subtalar" joint, called sprains, are very present at the sportive universe. In the indoor soccer, commonly practiced in our country, the sprains by the ankle inversion is between the injuries that happens more for the athletes at all levels of the practice because of the requirements imposed by the sport. Isokinetic evaluations have been used in the medication of muscular performance with the intention of getting more precise data about the strength produced by different muscular groups. The torque and activation ratios are two variables that can be measured in these tests, serving as parameter to detect possible muscular unbalance between agonist/antagonist muscles. This paper sought to evaluate the torque and activation ratios, and the power and muscular work done by the evertor and invertor ankle musculature, in indoor soccer players as well. Thirteen athletes were evaluated, seven of them that have unilateral ankle injury, were used to compare the injured and the healthy member. The torque and activation ratios at the evertor and invertor ankle musculature were evaluated during maximum voluntary isometrics contractions at the angles of -20º inversion, 0o and 20º eversion, and concentric and eccentric isokinetics at the velocities of 60º 120º and 180º/s. The work and power variables were also obtained in this tests. The torque ratio were obtained by dividing the evertor torque peak by the invertor torque peak, and the activation ratio by the same way, but dividing the RMS value by the EMG signal from the Short and Long Fibular Muscles Evertor by the Previous Tibial Muscle Invertor. The values found at the conventional and functional torque ratios, not showed significant differences between injured and health ankles, except for the invertor functional ratio EVexc/INVcon, which we found bigger values at the injured group, and this points for an unbalance at the Ev/Inv relation. The activation ratio not showed significant difference between the groups. But the power and work variables were equivalents in both groups, which demonstrate that after these athletes injures and the recuperations, and with the returning to the sportive activities, there were an reestablishing at the production of the muscular strength that actuate in the evertor and invetor ankle musculature.

As lesões de tornozelo, mais precisamente na articulação subtalar, chamadas de entorses, estão bastante presentes no âmbito esportivo. No futsal, esporte amplamente praticado em nosso país, a entorse por inversão do tornozelo está entre as lesões que mais acometem os atletas em todos os níveis de sua prática devido às exigências que o esporte impõe. Avaliações isocinéticas têm sido utilizadas na medição de performances musculares com o intuído de se obterem dados mais precisos em relação às forças produzidas por diferentes grupos musculares. A razão de torque e ativação são duas variáveis que podem ser medidas nestes testes servindo como parâmetro para detectar possíveis desequilíbrios musculares entre músculos agonistas/antagonistas. Este trabalho buscou avaliar as razões de torque e ativação, bem como a potência e o trabalho musculares realizados pela musculatura eversora e inversora do tornozelo em atletas de uma equipe de futsal. Foram avaliados 13 atletas, dos quais 7 atletas com lesão unilateral de tornozelo serviram de amostra para uma comparação entre o membro lesado e não lesado. As razões de torque e ativação da musculatura eversora e inversora do tornozelo foram avaliadas durante contrações isométricas voluntárias máximas nos ângulos de -20º de inversão, 0º e 20º de eversão, e isocinéticas concêntricas e excêntricas nas velocidades de 60º, 120º e 180º/s. As variáveis de trabalho e potência também foram obtidas nestes testes. As razões de torque foram obtidas com a divisão dos valores do pico de torque eversor pelo pico de torque inversor, e as razões de ativação da mesma forma, porém dividindo o valor RMS do sinal EMG dos músculos eversores Fibular Curto e Fibular Longo pelo músculo inversor Tibial Anterior. Os valores encontrados nas razões de torque convencionais e funcionais não demonstraram diferenças significativas entre o grupo de tornozelos com e sem lesão, com exceção da razão funcional inversora EVexc/INVcon, na qual foram encontrados valores maiores no grupo lesado, o que indica possível desequilíbrio na relação Ev/Inv. As razões de ativação não mostraram diferenças significativas entre os dois grupos. Já as variáveis trabalho e potência foram equivalentes nos dois grupos, o que demonstra que após a lesão e a recuperação destes atletas, e com a volta as atividades esportivas houve um reestabelecimento na produção das forças musculares que atuam na musculatura eversora e inversora do tornozelo. / The ankle injuries, more precisely in "subtalar" joint, called sprains, are very present at the sportive universe. In the indoor soccer, commonly practiced in our country, the sprains by the ankle inversion is between the injuries that happens more for the athletes at all levels of the practice because of the requirements imposed by the sport. Isokinetic evaluations have been used in the medication of muscular performance with the intention of getting more precise data about the strength produced by different muscular groups. The torque and activation ratios are two variables that can be measured in these tests, serving as parameter to detect possible muscular unbalance between agonist/antagonist muscles. This paper sought to evaluate the torque and activation ratios, and the power and muscular work done by the evertor and invertor ankle musculature, in indoor soccer players as well. Thirteen athletes were evaluated, seven of them that have unilateral ankle injury, were used to compare the injured and the healthy member. The torque and activation ratios at the evertor and invertor ankle musculature were evaluated during maximum voluntary isometrics contractions at the angles of -20º inversion, 0o and 20º eversion, and concentric and eccentric isokinetics at the velocities of 60º 120º and 180º/s. The work and power variables were also obtained in this tests. The torque ratio were obtained by dividing the evertor torque peak by the invertor torque peak, and the activation ratio by the same way, but dividing the RMS value by the EMG signal from the Short and Long Fibular Muscles Evertor by the Previous Tibial Muscle Invertor. The values found at the conventional and functional torque ratios, not showed significant differences between injured and health ankles, except for the invertor functional ratio EVexc/INVcon, which we found bigger values at the injured group, and this points for an unbalance at the Ev/Inv relation. The activation ratio not showed significant difference between the groups. But the power and work variables were equivalents in both groups, which demonstrate that after these athletes injures and the recuperations, and with the returning to the sportive activities, there were an reestablishing at the production of the muscular strength that actuate in the evertor and invetor ankle musculature.

As lesões de tornozelo, mais precisamente na articulação subtalar, chamadas de entorses, estão bastante presentes no âmbito esportivo. No futsal, esporte amplamente praticado em nosso país, a entorse por inversão do tornozelo está entre as lesões que mais acometem os atletas em todos os níveis de sua prática devido às exigências que o esporte impõe. Avaliações isocinéticas têm sido utilizadas na medição de performances musculares com o intuído de se obterem dados mais precisos em relação às forças produzidas por diferentes grupos musculares. A razão de torque e ativação são duas variáveis que podem ser medidas nestes testes servindo como parâmetro para detectar possíveis desequilíbrios musculares entre músculos agonistas/antagonistas. Este trabalho buscou avaliar as razões de torque e ativação, bem como a potência e o trabalho musculares realizados pela musculatura eversora e inversora do tornozelo em atletas de uma equipe de futsal. Foram avaliados 13 atletas, dos quais 7 atletas com lesão unilateral de tornozelo serviram de amostra para uma comparação entre o membro lesado e não lesado. As razões de torque e ativação da musculatura eversora e inversora do tornozelo foram avaliadas durante contrações isométricas voluntárias máximas nos ângulos de -20º de inversão, 0º e 20º de eversão, e isocinéticas concêntricas e excêntricas nas velocidades de 60º, 120º e 180º/s. As variáveis de trabalho e potência também foram obtidas nestes testes. As razões de torque foram obtidas com a divisão dos valores do pico de torque eversor pelo pico de torque inversor, e as razões de ativação da mesma forma, porém dividindo o valor RMS do sinal EMG dos músculos eversores Fibular Curto e Fibular Longo pelo músculo inversor Tibial Anterior. Os valores encontrados nas razões de torque convencionais e funcionais não demonstraram diferenças significativas entre o grupo de tornozelos com e sem lesão, com exceção da razão funcional inversora EVexc/INVcon, na qual foram encontrados valores maiores no grupo lesado, o que indica possível desequilíbrio na relação Ev/Inv. As razões de ativação não mostraram diferenças significativas entre os dois grupos. Já as variáveis trabalho e potência foram equivalentes nos dois grupos, o que demonstra que após a lesão e a recuperação destes atletas, e com a volta as atividades esportivas houve um reestabelecimento na produção das forças musculares que atuam na musculatura eversora e inversora do tornozelo. / The ankle injuries, more precisely in "subtalar" joint, called sprains, are very present at the sportive universe. In the indoor soccer, commonly practiced in our country, the sprains by the ankle inversion is between the injuries that happens more for the athletes at all levels of the practice because of the requirements imposed by the sport. Isokinetic evaluations have been used in the medication of muscular performance with the intention of getting more precise data about the strength produced by different muscular groups. The torque and activation ratios are two variables that can be measured in these tests, serving as parameter to detect possible muscular unbalance between agonist/antagonist muscles. This paper sought to evaluate the torque and activation ratios, and the power and muscular work done by the evertor and invertor ankle musculature, in indoor soccer players as well. Thirteen athletes were evaluated, seven of them that have unilateral ankle injury, were used to compare the injured and the healthy member. The torque and activation ratios at the evertor and invertor ankle musculature were evaluated during maximum voluntary isometrics contractions at the angles of -20º inversion, 0o and 20º eversion, and concentric and eccentric isokinetics at the velocities of 60º 120º and 180º/s. The work and power variables were also obtained in this tests. The torque ratio were obtained by dividing the evertor torque peak by the invertor torque peak, and the activation ratio by the same way, but dividing the RMS value by the EMG signal from the Short and Long Fibular Muscles Evertor by the Previous Tibial Muscle Invertor. The values found at the conventional and functional torque ratios, not showed significant differences between injured and health ankles, except for the invertor functional ratio EVexc/INVcon, which we found bigger values at the injured group, and this points for an unbalance at the Ev/Inv relation. The activation ratio not showed significant difference between the groups. But the power and work variables were equivalents in both groups, which demonstrate that after these athletes injures and the recuperations, and with the returning to the sportive activities, there were an reestablishing at the production of the muscular strength that actuate in the evertor and invetor ankle musculature.

The research presented in this thesis regards walking of quadruped robots, and particularly the walking of the Warp1 robot. The motivation for the robot is to provide a platform for autonomous walking in rough terrain. The thesis contains six papers ranging from development tools to actuation of robot legs. The first paper describes the methods and tools made for control development. These tools feature: programming of the robot without low level coding (C-code); that the controller has to be built only once for simulation and experiments; and that names of variables and constants are unchanged through the chain of software Maple -- Matlab -- Simulink -- Real~Time~Workshop -- xPC--Target. Three controllers, each making the robot walk are presented. The first controller makes the robot walk using the crawl gait. The method uses static stability as method for keeping balance and the instantaneous trunk motions are given by a concept using the so called weight ratios. A method for planning new footholds based on the positions of the existing footholds is also proposed and the controller experimentally verified. The second walking controller shows that the robot also can walk dynamically using the trot gait. The method proposed uses information from ground contact sensors on the feet as input to control balance, instead of, which is common, inertial sensors. It is experimentally verified that Warp1 can trot from level ground onto a slope and turn around while staying balanced. The main ideas of these two walking controllers are fused in the third which enables smooth transitions between crawl and trot. The idea of using the ground contact sensors from the first controller is here used to estimate the position of the center of mass. This controller uses weight ratios in the gait crawl as well as in the dynamic gait trot. Hence, the method of using weight ratios is not only useful for static stability for which it was originally intended. The controller is experimentally verified on Warp1. The Warp1 robot weighs about 60 kg, has 0.6 m long legs with three actuated joints on each. The speed and strength is sufficient only for slow walking, even though the installed power indicates that it should be enough for faster walking. The reason is that a walking robot often needs to be strong but slow when the feet are on the ground and the opposite when in the air. This can not be achieved with the motors and transmissions currently used. A transmission called the passively variable transmission (PVT) is proposed which enhance motor capabilities of robot joints. It is elastic, nonlinear and conservative. Some general properties for elastic transmissions are derived such that they can be compared with conventional transmissions. The PVT gives strong actuation at large loads and fast actuation at small loads. The proposed transmission is compared to a conventional transmission for a specific task, and the result is that a smaller motor can be used. / QC 20100831