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The use of rotary winged unmanned aerial vehicles in military and civilian applications is rapidly increasing. The primary objective of this study is to develop an automatic flight control system for a radio controlled (RC) helicopter. There is a need for a simple, easy to use methodology to develop automatic flight controllers for first-flight. In order to make the work accessible to new research groups without physical helicopter platforms, a simulation environment is created for validation. The size 30 RC helicopter in AeroSIMRC is treated as the final target platform. A grey box, timedomain system identification method is used to estimate a linear state space model that operates around hover. Identifying the unknown parameters in the model is highly dependent on the initial guess values and the input data. The model is divided into subsystems to make estimation possible. A cascaded controller approach is followed. The helicopter’s fast angular dynamics are separated from the slower translational dynamics. A linear quadratic regulator is used to control the helicopter’s attitude dynamics. An optimised PID outer-loop generates attitude commands from a given inertial position trajectory. The PID controllers are optimised using a simplex search method. An observer estimates the unmeasured states such as blade flapping. The controller is developed in Simulink®, and a plug-in written for AeroSIMRC enables Simulink® to control the simulator through a UDP interface to validate the model and controller. The identified state space model is able to accurately model the flight data from the simulator. The controllers perform well, keeping the helicopter stable even in the presence of considerable disturbances. The attitude controller’s performance is validated using an aeronautical design standard (ADS-33E-PRF) for handling qualities. The trajectory tracking is validated in a series of simulator flight tests. The linear controller is able to sustain stable flight in constant winds of up to 60% of the helicopter’s maximum airspeed. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2014

The use of rotary winged unmanned aerial vehicles in military and civilian applications is rapidly increasing. The primary objective of this study is to develop an automatic flight control system for a radio controlled (RC) helicopter. There is a need for a simple, easy to use methodology to develop automatic flight controllers for first-flight. In order to make the work accessible to new research groups without physical helicopter platforms, a simulation environment is created for validation. The size 30 RC helicopter in AeroSIMRC is treated as the final target platform. A grey box, timedomain system identification method is used to estimate a linear state space model that operates around hover. Identifying the unknown parameters in the model is highly dependent on the initial guess values and the input data. The model is divided into subsystems to make estimation possible. A cascaded controller approach is followed. The helicopter’s fast angular dynamics are separated from the slower translational dynamics. A linear quadratic regulator is used to control the helicopter’s attitude dynamics. An optimised PID outer-loop generates attitude commands from a given inertial position trajectory. The PID controllers are optimised using a simplex search method. An observer estimates the unmeasured states such as blade flapping. The controller is developed in Simulink®, and a plug-in written for AeroSIMRC enables Simulink® to control the simulator through a UDP interface to validate the model and controller. The identified state space model is able to accurately model the flight data from the simulator. The controllers perform well, keeping the helicopter stable even in the presence of considerable disturbances. The attitude controller’s performance is validated using an aeronautical design standard (ADS-33E-PRF) for handling qualities. The trajectory tracking is validated in a series of simulator flight tests. The linear controller is able to sustain stable flight in constant winds of up to 60% of the helicopter’s maximum airspeed. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2014

Este trabalho trata da modelagem e controle do radiotelescópio de Itapetinga (Atibaia, SP). Ele compreende não só síntese dos modelos e sintonia dos controladores, mas também identificação de sistemas, validação experimental de modelo e controle, reespecificação de componentes, sugestão de nova arquitetura de automação e controle e direcionamento do desenvolvimento que deve ser feito em futuros trabalhos. A parte inicial desta dissertação trata dos principais conceitos envolvidos e do levantamento de informações preliminares para a compreensão do sistema a ser modelado. A seguir é feita a modelagem matemática dos diversos componentes que formam os sistemas de posicionamento dos eixos de elevação e azimute. São então identificados experimentalmente os coeficientes matemáticos dos modelos e são feitas suas validações experimentais. Os controladores PID são sintonizados, baseados na simulação das malhas de controle através das ferramentas matemáticas MATLAB e Simulink. A validação experimental dos controladores é feita e comparada ao sistema de controle atual. São feitos os encaminhamentos das definições de novos motores e amplificadores e desenvolvida uma nova proposta de arquitetura para controle e supervisão do radiotelescópio, dando a ele funcionalidades muito além das que existem atualmente. Finalmente é dado o direcionamento dos próximos passos de desenvolvimento dos modelos, controladores e arquitetura de controle. Com este trabalho procura-se aumentar significativamente o entendimento do sistema de posicionamento do radiotelescópio, criando novos horizontes para o controle, operação, supervisão e manutenção do mesmo. / This work covers the modeling and control of the radio telescope of Itapetinga (Atibaia, SP). It tackles not only model synthesis and controllers tuning, but also system identification, experimental validation of model and control, re-specification of components, as well as a suggestion of a new automation and control architecture, and suggestions for future works. The initial part of this dissertation covers the main concepts and preliminary information for the understanding of the system to be modeled. Then a math model of the several components that form the pointing systems of the elevation and azimuth axis is done, followed by the experimental identification and validation of the math coefficients for the model. PID controllers are tuned based on the simulation of control loops using the math tools MATLAB and Simulink. Then the experimental validation of the controllers is done and compared to the current system control. Preliminary definitions of new motors and amplifiers are suggested, and a new proposal of architecture for radio telescope\'s control and supervision is developed, expanding its functionalities far beyond the ones available today. Finally, directions for the next steps to be taken in order to develop models, controllers and control architecture are given. This work aims to greatly increase the understanding of the radio telescope\'s pointing system, creating new horizons for its control, operation, supervision and maintenance.

Gao Jianjun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 75-76). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Solution Framework Using Dynamic Programming --- p.7 / Chapter 2.1 --- Difficulty of using dynamic programming --- p.8 / Chapter 2.2 --- Scalar-state problems --- p.12 / Chapter 2.3 --- Time-invariant system --- p.17 / Chapter 2.4 --- Illustrative example of a scalar-state problem --- p.21 / Chapter 3 --- Cardinality Constrained Quadratic Optimization --- p.26 / Chapter 3.1 --- Reformulation --- p.27 / Chapter 3.2 --- NP hardness --- p.31 / Chapter 3.3 --- Solving CCQP with an efficient branch and bound method --- p.34 / Chapter 3.3.1 --- Efficient branch and bound algorithm --- p.34 / Chapter 3.3.2 --- Geometrical interpretation of the proposed ranking order --- p.48 / Chapter 3.3.3 --- Additional algorithmic ideas for enhancing computational efficiency --- p.56 / Chapter 3.4 --- Numerical example and computational results --- p.60 / Chapter 4 --- Summary and Future Work --- p.73

Although cardinality constraints naturally arise in many applications, e.g., in portfolio selection problems of choosing small number of assets from a large pool of stocks or dynamic portfolio selection problems with limited trading dates within a given time horizon and in subset selection of the regression analysis, the state-of-the-art in cardinality constrained optimization has been stagnant up to this stage, largely due to the inherent combinatorial nature of such hard problems. We focus in this research on developing efficient and implementable solution algorithms for cardinality constrained optimization by investigating prominent structures and hidden properties of such problems. More specifically, we develop solution algorithms for four specific cardinality constrained optimization problems, including (i) the cardinality constrained linear-quadratic control problem, (ii) the optimal control problem of linear switched system with limited number of switching, (iii) the time cardinality constrained dynamic mean- variance portfolio selection problem, and (iv) cardinality constrained quadratic optimization problem. Taking advantages of a linear-quadratic structure of cardinality constrained optimization problems, we strive for analytical solutions when possible. More specifically, we derive an analytical solution for problem (iii) and obtain for both problems (i) and (ii) semi-analytical expressions of the solution governed by a family of Ricatti-like equations, which still suffer an exponentially growing complexity. To achieve high-performance of the solution algorithm, we devise algorithms of a branch and bound (BnB) type with various tight and computationally-cheap lower bounds achieved by identifying suitable SDP formulations and by exploiting geometric properties of the problem. We demonstrate efficiency of our proposed solution schemes evidenced from numerical experiments and present a firm step-forward in tackling this long-standing challenge of cardinality constrained optimization. / Gao, Jianjun. / Adviser: Duan Li. / Source: Dissertation Abstracts International, Volume: 72-11, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 134-142). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Hu San-qing. / "December 2001." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (p. 181-192). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

A digital adaptive slope control (DASC) technique is presented to improve the dynamic response and efficiency of a current programmed mode (CPM) buck converter employing a low-cost auxiliary phase. Compared to the existing nonlinear control techniques, the advantages of the proposed control scheme include superior voltage droop and settling time, and on-line calibration to compensate for tolerance in the inductance. The proposed technique is experimentally verified on a 500 kHz, 10 V to 2.5 V CPM buck converter prototype. Charge balancing and optimal transient response are achieved for a range of positive and negative load steps. In addition, compared to a representative single phase converter, the proposed system not only has better dynamic response but also achieves 2 % heavy-load and 10 % light-load steady-state efficiency improvement. The impact of the auxiliary phase operation on the converter’s dynamic efficiency is also evaluated at different load step amplitudes and frequencies.

A digital adaptive slope control (DASC) technique is presented to improve the dynamic response and efficiency of a current programmed mode (CPM) buck converter employing a low-cost auxiliary phase. Compared to the existing nonlinear control techniques, the advantages of the proposed control scheme include superior voltage droop and settling time, and on-line calibration to compensate for tolerance in the inductance. The proposed technique is experimentally verified on a 500 kHz, 10 V to 2.5 V CPM buck converter prototype. Charge balancing and optimal transient response are achieved for a range of positive and negative load steps. In addition, compared to a representative single phase converter, the proposed system not only has better dynamic response but also achieves 2 % heavy-load and 10 % light-load steady-state efficiency improvement. The impact of the auxiliary phase operation on the converter’s dynamic efficiency is also evaluated at different load step amplitudes and frequencies.

University of Macau / Faculty of Science and Technology / Department of Mathematics