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The performance of smart structures depends on the electromechanical behaviour of piezoelectric sensors/actuators and the bonding condition along the interface, which connects the sensor/actuator and the host structures. This thesis documents a theoretical study of the influence of material parameters of the imperfect bonding layer on the coupled electromechanical characteristics of piezoelectric sensors/actuators. A one dimensional sensor/actuator model with an imperfect bonding layer, which undergoes a shear deformation, is proposed. The emphasis of the current study is on the local stress and strain fields near imperfectly bonded sensors/actuators and the load transfer. Analytical solutions based on the integral equation method are provided. Detailed numerical simulation is conducted to evaluate the influence of the geometry and the material mismatch of the adhesive layer upon the sensing/actuating process. The interfacial debonding and its effect upon the strain/stress distribution and the overall performance of the integrated structure are evaluated in detail.

This document presents a study of the numerical simulation of non-equilibrium plasma discharges in air mixtures in the atmospheric pressure regime. Such plasma is formed by applying a very high electric field over a very short time duration (nano-microsecond) which preferentially heats the electrons to very high temperatures (10 electron Volts or more) while preventing thermalization of the gas. Preferentially heating the electrons to very high temperatures allows the discharge to efficiently and rapidly ionize and dissociate the gas mixture without losing too much energy to thermalization or vibrational excitation. Consequently, two useful characteristics of these discharges are low gas temperatures and rapid electron chemistry. This study focuses on two applications of interest: ignition of fuel-air mixtures and plasma enhanced medicine. For ignition, there are two situations that arise where it is difficult for traditional spark ignition systems to operate. The first is at the supersonic flow regime where the residence time of the flow in the engine is low. The second is high pressure ignition of lean fuel-air mixtures. For plasma medicine and surface treatment, non-equilibrium plasma is an effective means of delivering reactive radical species to the surface while limiting damage due to thermal heating. The problems of interest are characterized by the formation of weakly ionized plasma in the presence of flow fields such as supersonic boundary layers or low speed jets. To simulate the coupled plasma-fluid flow physics of these discharges, two numerical tools are utilized. The first is a two-temperature, multiple species, self-consistent plasma solver with finite rate chemistry which is used to simulate the plasma as it forms in a neutral background gas. The second tool is a multiple-species compressible flow solver which calculates the flow field properties of the background gas mixture. / text

This thesis focuses on the development of a novel hybrid linear actuator (HLA). The research includes the optimal design, the particular fabrication, and the experimental validation. The principle of the HLA is based on the integration of the mechanisms of the solenoid actuator and the voice coil actuator. Such integration is achieved by a magnetic circuit consisting of a magnetic flux orientator, a permanent magnet, a composite shell, and a special coil. The HLA is capable of having a high repelling force at one end and a high attractive force at another end. A step-optimization technique is developed and used to determine the key parameters of the HLA, with the aid of sweeping functions in finite element analysis. Moreover, a single-pulse power supply is specially designed and prototyped for driving the HLA. The performance of the HLA is systematically characterized by simulations and experiments.

This thesis focuses on the development of a novel hybrid linear actuator (HLA). The research includes the optimal design, the particular fabrication, and the experimental validation. The principle of the HLA is based on the integration of the mechanisms of the solenoid actuator and the voice coil actuator. Such integration is achieved by a magnetic circuit consisting of a magnetic flux orientator, a permanent magnet, a composite shell, and a special coil. The HLA is capable of having a high repelling force at one end and a high attractive force at another end. A step-optimization technique is developed and used to determine the key parameters of the HLA, with the aid of sweeping functions in finite element analysis. Moreover, a single-pulse power supply is specially designed and prototyped for driving the HLA. The performance of the HLA is systematically characterized by simulations and experiments.

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The performance and broader application of dielectric barrier discharge (DBD) plasma actuators are restricted by the manufacturing methods currently employed. In the current work, two methodologies are proposed to build robust plasma actuators for active flow control; a protective silicone oil (PDMS) treatment for hand-cut and laid tape-based actuators and a microfabrication technique for glass-based devices. The microfabrication process, through which thin film electrodes are precisely deposited onto plasma-resistant glass substrates, is presented in detail. The resulting glass-based devices are characterized with respect to electrical properties and output for various operating conditions. The longevity of microfabricated devices is compared against silicone-treated and untreated hand-made devices of comparable geometries over 60 hours of continuous operation. Both tungsten and copper electrodes are considered for microfabricated devices. Human health effects are also considered in an electromagnetic field study of the area surrounding a live plasma actuator for various operating conditions.

The performance and broader application of dielectric barrier discharge (DBD) plasma actuators are restricted by the manufacturing methods currently employed. In the current work, two methodologies are proposed to build robust plasma actuators for active flow control; a protective silicone oil (PDMS) treatment for hand-cut and laid tape-based actuators and a microfabrication technique for glass-based devices. The microfabrication process, through which thin film electrodes are precisely deposited onto plasma-resistant glass substrates, is presented in detail. The resulting glass-based devices are characterized with respect to electrical properties and output for various operating conditions. The longevity of microfabricated devices is compared against silicone-treated and untreated hand-made devices of comparable geometries over 60 hours of continuous operation. Both tungsten and copper electrodes are considered for microfabricated devices. Human health effects are also considered in an electromagnetic field study of the area surrounding a live plasma actuator for various operating conditions.

This paper reports the findings of conceptual design and application research for a novel use of irrigation fluid power to provide mobility to a legged autonomous, tethered irrigation robot. Systems already exist to convert fluid power to rotary motion to power various irrigation systems. The conceptual designs implement a McKibben actuator to generate linear motion with water as the process fluid and a compact 3DOF spherical joint to create a modular robot leg that can be used to create a legged ambulatory robot. A six-legged robot is proposed from the conceptual design of the modular leg. Irrigation was selected as the initial leading application, however, once deployed the devices provide a field-ready platform to facilitate a whole suite of agriculturally important activities; seeding, weed suppression, pest management, soil sensing, crop growth assessment, as well as creating a robust research platform. This work is the lead in research to provide a viable mechanism to facilitate control system and dynamic modelling ahead of full-scale prototyping and field testing. / Graduate / 2021-04-08