Zhong, Renxin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 107-114). / Abstracts in English and Chinese. / Abstract --- p.iv / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Non-Minimum Phase Nonlinear Systems --- p.1 / Chapter 1.2 --- Robust Output Regulation Problem --- p.4 / Chapter 1.3 --- Global Robust Output Regulation for Non-Minimum Phase Nonlinear Systems in Lower Triangular Form --- p.6 / Chapter 1.4 --- Rotational/Translational Actuator System --- p.8 / Chapter 1.5 --- Organization and Contributions --- p.8 / Chapter 2 --- Global Robust Output Regulation for Non-Minimum Phase Non-linear Systems in Lower Triangular Form --- p.10 / Chapter 2.1 --- Introduction --- p.10 / Chapter 2.2 --- Assumptions and Preliminaries --- p.12 / Chapter 2.3 --- Solvability Conditions --- p.17 / Chapter 2.4 --- Numerical Examples --- p.19 / Chapter 2.5 --- Concluding Remarks --- p.46 / Chapter 3 --- Global Robust Output Regulation for A Class of Non-Minimum Phase Nonlinear Systems by Output Feedback Control --- p.47 / Chapter 3.1 --- Introduction --- p.48 / Chapter 3.2 --- Assumptions and Preliminaries --- p.49 / Chapter 3.3 --- Reduced order observer design --- p.56 / Chapter 3.4 --- Stabilization of x system --- p.59 / Chapter 3.5 --- "Interconnection of the n,z,ζ,x subsystems and small gain condition" --- p.63 / Chapter 3.6 --- Numerical example --- p.67 / Chapter 3.7 --- Conclusion --- p.76 / Chapter 4 --- Robust output regulation for the nonlinear benchmark problem via output feedback --- p.77 / Chapter 4.1 --- Introduction --- p.78 / Chapter 4.2 --- Disturbance rejection problem of the RTAC system by output feedback control --- p.79 / Chapter 4.3 --- Robust Disturbance rejection problem of the RTAC system by output feedback --- p.88 / Chapter 4.4 --- Conclusion --- p.98 / Chapter 5 --- Conclusion --- p.103 / List of Figures --- p.105 / Bibliography --- p.107 / Biography --- p.115

This thesis is concerned with robust control of an offshore steel jacket platform subject to nonlinear wave-induced forces. Since time delay and uncertainty are inevitably encountered for an offshore structure and their existence may induce instability, oscillation and poor performance, it is very significant to study on how the delay and uncertainty affect the offshore structure. In this thesis, a memory robust control strategy is, for the first time, proposed to reduce the internal oscillations of the offshore structure under wave-induced forces, so as to ensure the safety and comfort of the offshore structure. Firstly, when the system's states are adopted as feedback, memory state feedback controllers are introduced for the offshore structure. By using Lyapunov-Krasovskii stability theory, some delay-dependent stability criteria have been established, based on which, and by combining with some linearization techniques, memory state feedback controllers are designed to control the offshore structure. The simulation results show that such controllers can effectively reduce the internal oscillations of the offshore structure subject to nonlinear wave-induced forces and uncertainties. On the other hand, a new Lyapunov-Krasovskii functional is introduced to derive a less conservative delay-dependent stability criterion. When this criterion is applied to the offshore structure, an improved memory state feedback controller with a small gain is obtained to control the system more effectively, which is sufficiently shown by the simulation. Secondly, when the system's outputs are adopted as feedback, memory dynamic output feedback controllers are considered for the offshore structure. By employing a projection theorem and a cone complementary linearization approach, memory dynamic output feedback controllers are derived by solving some nonlinear minimization problem subject to some linear matrix inequalities. The simulation results show that the internal oscillations of the offshore structure subject to nonlinear wave-induced forces are well attenuated. Finally, robust H control is fully investigated for the offshore structure. By employing Lyapunov-Krasovskii stability theory, some delay-dependent bounded real lemmas have been obtained, under which, via a memory state feedback controller or a dynamic output feedback controller, the resulting closed-loop system is not only asymptotically stable but also with a prescribed disturbance attenuation level. The simulation results illustrate the validity of the proposed method.

"The Department of Electrical and Computer Engineering, the University of Newcastle." Includes index. Bibliography: p. [137]-143.

<p>Force control is introduced to robots to solve the problem in machining applications due to the fact that the robot compliance might cause deviation between actual and desired robot path. Also large tolerances in the casting process as well as positioning errors from the clamping create deviations for which the force control technology can adept. Force control has also shown successful in automatic learning of paths along non linear surfaces.</p><p>This study investigates the possibility of introducing robots equipped with force control at Volvo Aero Corporation in order to robotize polishing and deburring processes. These are today performed by manual labor. This study investigates more specifically the ABB Force Control machining application package. The polishing process has shown to be very complex and today’s version of the ABB force control package cannot give sufficiently robust results to be recommended for implementation. The major issue is the non-existing compliance of tool orientation needed to adapt to casting and positioning deviations due to varying work piece dimensions. The deburring process has however shown to be easier to handle, and a robot cell and methodology is proposed in this report.</p>

Multi-level decision feedback equalization (MDFE) is an effective technique to remove inter-symbol interference (ISI) from disk readback signals, which uses the simple architecture of decision feedback equalization. Parallelism which doubles the symbol rate can be realized by setting the first tap of the feedback filter to zero. A mixed-signal implementation has been chosen for the parallel MDFE, in which coefficients for the 9-tap feedback filter are adapted in the digital domain by 10-bit up/ down counters; 6-bit current mode D/A converters are used to convert digital coefficients to differential current signals which are summed with the forward equalizer (FE) output, and a flash A/D is used to make decisions and generate error signals for adaptation. In this thesis, a description of the parallel structure and the adaptation algorithm are presented with behavioral level verification. The circuit design and layout were carried out in HP 1.2um n-well CMOS process. The design of the high-speed counter and the current-mode D/A are discussed. HSPICE simulations show that a symbol rate of 100Mb/s for the feedback equalizer is readily achieved. / Graduation date: 1997

Decision feedback equalizer (DFE) is an effective method to remove inter-symbol interference (ISI) from a disk-drive read channel. Analog IC implementations of DFE potentially offers higher speed, smaller die area, and lower power consumption when compared to their digital counterparts. Most of the available DFE equalizers were realized by using digital FIR filters preceded by a flash A/D converter. Both the FIR filter and flash A/D converter are the major contributers to the power dissipation. However, this project focuses on the analog IC implementations of the DFE to achieve high speed and low power consumption. In other words, this project gets intensively involved in the design of a large-input highly-linear voltage-to-current converter, the design of a high-speed low-power 6-bit comparator, and the design of a high-speed low-power 6-bit current-steering D/A converter. The design and layout for the proposed analog equalizer are carried out in a 1.2 pm n-well CMOS process. HSPICE simulations show that an analog DFE with 100 MHz clock frequency and 6-bit accuracy can be easily achieved. The power consumption for all the analog circuits is only about 24mW operating under a single 5V power supply. / Graduation date: 1997

Vision is a flexible, non-contact sensor that can be used for position feedback in closed-loop control of dynamic systems. Current vision systems for industrial automation provide low sample rates and large sample delays relative to other types of position sensors. Poor sample rates and sample delays are a result of the vast volume of data that must be collected and processed by the vision system. A predictive visual tracker can help compensate for some of the deficiencies of current industrial vision systems. The objectives of the present research are to demonstrate that vision is a useful feedback sensor and prediction can be used to improve performance by compensating for the feedback delay of the vision system. An inverted pendulum was stabilized using a vision sensor as feedback to a state-feedback controller. The vision data was run through a d-step ahead predictor to compensate for the vision system delays. The system was simulated in Mat lab and an actual physical system was used to test the performance of the control system. The inverted pendulum provides a good test-bed for studying predictive control using vision feedback. The pendulum will fall without the constant adjustment of the cart position. The adjustment of the cart by the controller is delayed because of latency and quantization errors in vision feedback. The better the controller is able to compensate for delays and quantization errors, the greater its ability to stabilize the inverted pendulum. / Graduation date: 1996

Graduation date: 1996

Michael Athans, Gunter Stein, Lena Valavani. / "December 31, 1985." / Bibliography: leaf 10. / NASA Grant NSG 2-297 MIT OSP no. 95178

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