In this thesis, a new Poly Phase Motor (rotary actuator) based on the Shape Memory Alloy (SMA) is presented. Details of Design, Modeling, Characterization, Realization and Control of Poly Phase SMA Motor are presented. Motor with 3 and 6 Phases, with appropriate Control circuit have been realized in laboratory and simulated results have been verified experimentally. In literature, broadly two types of Shape Memory Alloy based motors namely limited rotation motor and unlimited rotation motor are found. In the unlimited rotation type SMA based motor the SMA element is in the spring form. Hence, an attempt has been made in this research to develop an Unlimited Rotating type Balanced Poly Phase Motor based on SMA wire in series with a spring in each phase. By isolating SMA actuation and spring action a constant force by the SMA wire through out its range of operation is achieved. While designing the motor, similarity in function between Poly Phase SMA Motor and Stepper Motor was found. Hence, the Poly Phase Motor is characterized similar to that of a Stepper Motor. Functionally, the Poly Phase Motor can be used in stepping mode for generating incremental motion and servo mode for generating continuous motion. Various parameters of the motor have been defined. The motor can be actuated in either direction with different Phase sequencing methods, which are presented in this work. While explaining sequencing methods, effect of the thermal time constants has also been presented. The lumped thermal model is used for dynamic simulation of motor. The motor has been modeled with a new approach to the SMA wire Hysteresis model. This model is simple and useful for real time control applications. Model is implemented using Simulink and used for the simulation of the motor. Generalization of the motor concept is done and motor up to 16 Phases are studied and the simulation results done using MATLAB are discussed. It could be observed that the torque generated by the motor increases with increased number of phases while the torque ripple reduces. The motor torque ripple is better for motor with odd number of phases due to its construction. Two methods of achieving servo motion are presented. The first method is Micro Stepping, consisting of controlling single phase temperature with a position feedback. The second method is Antagonistic Control of temperatures of phases with position feedback. Both the above methods use PID Controller with optical encoder feedback for position sensing. Performance of the actuator with step, ramp and triangle inputs has been simulated using Simulink and verified experimentally for various loads and disturbances. Positional accuracy of 0.07% for the Step input and for the full rotation of 3600 is achieved. Vector Control of SMA Motor is presented. By this method Speed and the torque of the motor will be effectively controlled. Since the temperatures of the wires are controlled in this research, this method is named as Thermal Space Phasor or Vector Based Control. This method of rotation of motor is simulated using Simulink and verified experimentally. Here the current through the SMA is controlled so as to get near sinusoidal variation in temperature. This leads to a near Sinusoidal variation of force. It is shown that by controlling the temperature of phases Sinusoidally with a phase shift of 1200, the Resultant Force will be a constant over the Spatial angle of 3600 and its Velocity of rotation will be Constant. Open loop and closed loop control of the speed and torque is presented. While the motor rotates at fixed Speed and Torque in Open Loop Control, motor adopts to change in torque and velocity in Closed Loop control with reduced ripple. PID Controller is used for closed loop control. The presented rotary actuator and their experimental results set a new standard for SMA based new generation rotary actuators and control.

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The need for high performance circuits in systems with low-voltage and low-power requirements has exponentially increased during the few last years due to the sophistication and miniaturization of electronic components. Most of these circuits are required to have a very good efficiency behavior in order to extend the battery life of the device. This dissertation addresses two important topics concerning very high efficiency circuits with very high performance specifications. The first topic is the design and implementation of class D audio power amplifiers, keeping their inherent high efficiency characteristic while improving their linearity performance, reducing their quiescent power consumption, and minimizing the silicon area. The second topic is the design and implementation of switching voltage regulators and their controllers, to provide a low-cost, compact, high efficient and reliable power conversion for integrated circuits. The first part of this dissertation includes a short, although deep, analysis on class D amplifiers, their history, principles of operation, architectures, performance metrics, practical design considerations, and their present and future market distribution. Moreover, the harmonic distortion of open-loop class D amplifiers based on pulse-width modulation (PWM) is analyzed by applying the duty cycle variation technique for the most popular carrier waveforms giving an easy and practical analytic method to evaluate the class D amplifier distortion and determine its specifications for a given linearity requirement. Additionally, three class D amplifiers, with an architecture based on sliding mode control, are proposed, designed, fabricated and tested. The amplifiers make use of a hysteretic controller to avoid the need of complex overhead circuitry typically needed in other architectures to compensate non-idealities of practical implementations. The design of the amplifiers based on this technique is compact, small, reliable, and provides a performance comparable to the state-of-the-art class D amplifiers, but consumes only one tenth of quiescent power. This characteristic gives to the proposed amplifiers an advantage for applications with minimal power consumption and very high performance requirements. The second part of this dissertation presents the design, implementation, and testing of switching voltage regulators. It starts with a description and brief analysis on the power converters architectures. It outlines the advantages and drawbacks of the main topologies, discusses practical design considerations, and compares their current and future market distribution. Then, two different buck converters are proposed to overcome the most critical issue in switching voltage regulators: to provide a stable voltage supply for electronic devices, with good regulation voltage, high efficiency performance, and, most important, a minimum number of components. The first buck converter, which has been designed, fabricated and tested, is an integrated dual-output voltage regulator based on sliding mode control that provides a power efficiency comparable to the conventional solutions, but potentially saves silicon area and input filter components. The design is based on the idea of stacking traditional buck converters to provide multiple output voltages with the minimum number of switches. Finally, a fully integrated buck converter based on sliding mode control is proposed. The architecture integrates the external passive components to deliver a complete monolithic solution with minimal silicon area. The buck converter employs a poly-phase structure to minimize the output current ripple and a hysteretic controller to avoid the generation of an additional high frequency carrier waveform needed in conventional solutions. The simulated results are comparable to the state-of-the-art works even with no additional post-fabrication process to improve the converter performance.