Thesis (Ph. D.)--Johns Hopkins University. / Vita. Includes bibliographical references.

Thesis (M.Sc.). / Written for the Dept. of Mathematics and Statistics. Title from title page of PDF (viewed 2009/06/25). Includes bibliographical references.

No description available.

It was P. Alexandroff and P. Urysohn who first introduced the class of H-closed spaces. Since then, it has evoked the interest of many topologists. The concept of H-closedness is closely related to that of compactness, and it is for this reason that attempts have been made to see what theorems about compactness hold for H-closedness. Miroslav Katetov constructed an analogue to the Stone-tech cornpactification, which is the Katetov H-closed extension.

In the last few decades, miniaturization has been in increasing demand in many applications. The miniature actuators should comprise high power-weight ratio while having a fast dynamic response, and high efficiency. In this thesis several approaches have been studied to develop a low pressure water hydraulic system driving a miniature rotary joint as the end-effecter. While the system was expected to have a cross sectional diameter of 15 mm, two prototypes were manufactured having cross sections of 12.5 mm X 13 mm (18 mm dia.) and 16 mm X 18 mm (24 mm dia.). The system involves a novel closed-circuit water hydraulic system in which a controlled volume of water supplied by a motor-cylinder pump drives the rotary joint cylinders (4 mm bore). The linear motion of these cylinders is converted to a rotational motion through a sliders-pulley mechanism. The rotation of an arm attached to this pulley is measured by a magnetic rotary encoder. The dynamic behaviour of the system was studied and the most important parameters have been modelled. This model has been utilized in the design of a model based feedforward (FFWD) controller which was added to a PID controller to enhance the position control of the rotary arm. Numerous experiments were conducted with the horizontal rotation of the rotary arm. The maximum error ( emax) recorded for a mixed input (a combination of rising and falling cycloidals of 120° and 60° with pause periods of 1 and 0.5 s) with a PID controller was 8.3° while with the addition of the FFWD term this dropped to 6.2°. The maximum root mean square error (RMSE) for the same trajectory has been 1.7° and 0.9° for PID and FFWD+PID controllers respectively. The steady state error (SSE) which was measured during a eycloidal input of 120° was recorded to be in the range of ±0.2° for both of the controllers. The robustness of the controllers was evaluated by adding a mass of 8.5 g to the end of the rotary arm which produced an un-modelled extra large inertia to the system dynamic when the arm rotating horizontally. Robustness of both controllers was demonstrated as the change in the main numerical performance indicators (RMSE, ernax, and SSE) were not remarkable. Another set of experiments performed with the rotary joint positioned vertically introduced with an un-modelled changing force. The numerical performance indicators were almost unchanged again. A comparison between the results of this thesis with the ones from the previous work in our laboratory by R. Sindrey indicates a significant improvement. / Thesis / Master of Applied Science (MASc)

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This thesis presents the design of various closed-loop real-time control of a novel linear magnetostrictive actuator. The novel linear magnetostrictive actuator which uses Terfenol-D as the magnetostrictive material was developed by Sadighi. It solves the problem of power consumption in a conventional magnetostrictive actuator. However, the control system of this magnetostrictive actuator cannot control the current in the coils, which limits the performances of the real-time position control. In the closed-loop real-time control system proposed in this thesis, the controller is designed depending on the change of current. The closed-loop real-time control design focused on the position control of the active element in the novel linear magnetostrictive actuator. The closed-loop position-control system of the linear magnetostrictive actuator was successfully designed by implementing a closed-loop current-control system as an inner loop of the entire control system. This design offers the flexibility to design various position controllers in the closed-loop position-control system. The closed-loop current-control design uses pulse-width modulation (PWM) signal to change the current in the coils of the novel linear magnetostrictive actuator. By changing the duty ratio of the PWM signal, the current in the coils can be changed from zero to its maximum value. With a current controller using an integrator with a gain of 10, the current can be controlled with high response time and an error of /- 0.01 A. The position-controller design was successfully conducted by using four different approaches. First, a proportional-integral-derivative (PID) controller which was designed by relay-auto tuning method with experiments exhibited a position error of ±1 μm with a 5 μm peak-to-peak position noise. Second, a PID controller which was designed by root-locus can control the position with a position error of /- 3-4 μm with a 5 μm peak-to-peak position noise. Third, a linear variable velocity controller exhibited a position error of /-5 μm with a 5 mu m peak-to-peak position noise. Then, the sliding mode control (SMC) exhibited a position error of /-5 μm with a 5 μm peak-to-peak position noise.

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