The advantages of UAVs in the aviation arena have led to extensive research activities on autonomous technology of UAVs to achieve specific mission objectives. This thesis mainly focuses on the development of a mission-based guidance system. Among various missions expected of UAVs for future needs, autonomous formation flight (AFF) and obstacle avoidance within safe operation limits are investigated. In the design of an adaptive guidance system for AFF, the leader information except position is assumed to be unknown to a follower. Thus, the only measured information related to the leader is the line-of-sight range and angle. Adding an adaptive element with neural networks into the guidance system provides a capability to effectively handle leader's velocity changes. Therefore, this method can be applied to the AFF control systems that use passive sensing methods. The simulation and flight test results clearly show that the adaptive guidance control system is a promising solution for autonomous formation flight of UAVs. The successful flight evaluations using the GTMax rotary wing UAV also demonstrate unique maneuvering aspects associated with rotary wing UAVs in formation flight. In the design of an autonomous obstacle avoidance system, an integrated approach is proposed to resolve the conflict between aggressive maneuvering needed for obstacle avoidance and the constrained maneuvering needed for envelope protection. A time-optimal problem with obstacle and envelope constraints is used for an integrated approach for obstacle avoidance and envelope protection. The Nonlinear trajectory generator (NTG) is used as a real-time optimization solver. The computational complexity arising from the obstacle constraints is reduced by converting the obstacle constraints into a safe waypoint constraint along with an implicit requirement that the horizontal velocity during the avoidance maneuver must be non-negative. The issue of when to initiate a time-optimal avoidance maneuver is addressed by including a requirement that the vehicle must maintain its original flight path to the maximum extent possible. The simulation results using a rotary wing UAV demonstrate the feasibility of the proposed approach for obstacle avoidance with envelope protection.

Made available in DSpace on 2014-12-17T14:55:45Z (GMT). No. of bitstreams: 1 RaphaellMS_DISSERT.pdf: 3087457 bytes, checksum: 184208141b97a58de312de245a6bd3e8 (MD5) Previous issue date: 2011-02-11 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Conventional control strategies used in shunt active power filters (SAPF) employs real-time instantaneous harmonic detection schemes which is usually implements with digital filters. This increase the number of current sensors on the filter structure which results in high costs. Furthermore, these detection schemes introduce time delays which can deteriorate the harmonic compensation performance. Differently from the conventional control schemes, this paper proposes a non-standard control strategy which indirectly regulates the phase currents of the power mains. The reference currents of system are generated by the dc-link voltage controller and is based on the active power balance of SAPF system. The reference currents are aligned to the phase angle of the power mains voltage vector which is obtained by using a dq phase locked loop (PLL) system. The current control strategy is implemented by an adaptive pole placement control strategy integrated to a variable structure control scheme (VS?APPC). In the VS?APPC, the internal model principle (IMP) of reference currents is used for achieving the zero steady state tracking error of the power system currents. This forces the phase current of the system mains to be sinusoidal with low harmonics content. Moreover, the current controllers are implemented on the stationary reference frame to avoid transformations to the mains voltage vector reference coordinates. This proposed current control strategy enhance the performance of SAPF with fast transient response and robustness to parametric uncertainties. Experimental results are showing for determining the effectiveness of SAPF proposed control system / Resumo: As estrat?gias de controle convencionais de filtros ativos de pot?ncia paralelos (FAPP) empregam esquemas de detec??o de harm?nicos em tempo real, usualmente implementados com filtros digitais. Isso aumenta o n?mero de sensores na estrutura do filtro, o que resulta em altos custos. Al?m disso, esses esquemas de detec??o introduzem atrasos que podem deteriorar o desempenho da compensa??o de harm?nicos. Diferentemente dos esquemas de controle convencionais, este artigo prop?e uma nova estrat?gia de controle que regula indiretamente as correntes de fase da rede el?trica. As correntes de refer?ncia do sistema s?o geradas pelo controle de tens?o do barramento CC e s?o baseadas no balan?o de pot?ncia ativa do sistema FAPP. As correntes de refer?ncia s?o alinhadas com o ?ngulo de fase do vetor tens?o da rede, que ? obtido usando um PLL (Phase Locked Loop). O controle de corrente ? implementado por uma estrat?gia de controle adaptativo por aloca??o de p?los, integrada com um esquema de controle com estrutura vari?vel (VS?APPC). No VS?APPC, o princ?pio do modelo interno (IMP) de refer?ncia ? usado para eliminar o erro em regime permanente das correntes do sistema. Isso for?a as correntes de fase do sistema a serem senoidais e com baixo teor de harm?nicos. Al?m disso, os controladores de corrente s?o implementados no referencial estacion?rio para evitar transforma??es nas coordenadas de refer?ncia do vetor tens?o da rede. Esta estrat?gia de controle de corrente melhora a performance do FAPP com uma resposta transit?ria r?pida e robustez a incertezas param?tricas. Resultados experimentais s?o mostrados para demonstrar a efic?cia do sistema de controle proposto para o FAPP