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In this paper, the need to develop a control strategy and test apparatus for next generation hybrid vehicles was realized. The complexity of today’s and future hybrid vehicles necessitates the need for an equally advanced method of control that can extract the optimal fuel economy from the system as a whole. A review of existing hybrid vehicle control strategies was performed. Overall, much research has been done on the optimization of series and parallel type vehicles, but virtually no information was found on the optimal use of advanced powersplit drivetrains. However, the control strategy concepts explored in the literature are useful, and can be extended to complex architectures like the General Motors Two-Mode design. The equivalent consumption minimization strategy (ECMS) method developed by Rizzoni et al at the Ohio State University has proven to be a well developed control strategy that has seen much progress over the last decade. Although it has been only demonstrated on parallel-type vehicles, it was chosen as the basis for the control strategy methodology. An in-depth analysis on the Two-Mode transmission operation was performed. The fundamental equations for each of its range states were derived for future use in developing a plant model, and for use in control strategy development. The torque and speed capabilities of each of its modes and gears were analysed. A detailed plant model was created to form a virtual test bed for control strategy development purposes. The models use empirical data provided by manufactures, which ensures a reasonable level of accuracy in portraying component constraints and efficiencies. Building on the ECMS, a similar hybrid vehicle control strategy was developed for Two-Mode transmission based vehicles. It was modified to handle two degrees of freedom as required by the system. Its objective is to constantly minimize the total equivalent power use in the system which is defined as the sum of the chemical power in the fuel and the power used by the battery multiplied by an equivalency factor. Overall, the control strategy provides a strong basis for the optimal control of nextgeneration hybrid vehicles incorporating powersplit transmissions. It is suggested that further research be explored in combining rule-based control methods with the developed optimization based method since rule-based methods can add the stability required for enhanced drivability. / Graduate / 10000-01-01

The building sector is a one of modern society’s biggest users of energy. In turn, a building’s windows have a significant impact on its energy usage. Electrochromic windows have a thin film on one of the panes, designed to variably change the tint of the window. Thereby the solar heat gain, needed internal lighting and building energy utilization are varied. This thesis uses the simulation software IDA ICE 4.5 to simulate control scenarios for electrochromic windows. The goal is to examine how well this software can simulate the windows as well as to explore the potential of creating custom control algorithms for the windows. The impact of the control scenarios on the energy consumption of a building is then analyzed. The reference case for the simulations is a regular window with blinds, where the blinds are controlled with a built-in algorithm. The simulated control scenarios for the electrochromic windows were; the built-in algorithm, always off, always on, operative temperature, workplane illuminance, and light levels at the façade and window. In the simulation results the energy usage was slightly lowered with the electrochromic windows using the built-in control compared to the reference case. The custom algorithm that uses the light levels at the façade and window was designed to improve upon the built-in algorithm with additional adjustable settings. However, this custom algorithm produced similar results to the built-in algorithm and the majority of the additional settings had little impact on the energy usage. The other custom designed algorithms measured workplane illuminance and operative temperature to control the shading. These showed an overall decrease in the energy usage compared to the reference case. The IDA ICE software has potential for further simulations of a building’s energy usage while using electrochromic windows. Further investigation is needed to determine if the simulation resolution is high enough to accurately depict the effect these settings might have on the energy usage.

This thesis presents an electrical system analysis of a wave energy converter (WEC) for the objective of grid connection. To transfer the enormous amount of power from waves to the load centers, efficient power electronic systems are essential. This thesis includes the modeling of a buoy–translator dynamics and the modeling of a linear permanent magnet generator along with simulation and experimental validation. Diode bridge rectifiers are considered for rectification to avoid the complex linear generator control at the input side. To reduce the size and the cost of energy storage elements, DC voltage regulation is done using a DC/DC converter. To achieve smooth and high power, many WECs need to be connected to a common DC link. A neutral point clamped inverter is considered for the DC/AC conversion due to its advantages over conventional topologies. Various pulse width modulation schemes are tested for the inverter to choose the optimum PWM method. The harmonics in the inverter output voltage is derived numerically and compared with simulation and experiment to understand the effect of dead-time in the inverter operation. Depending on the load current drawn from the inverter, the voltages in the two input capacitors of a three-level neutral point clamped inverter deviates from equilibrium unless the neutral point is grounded. To avoid this voltage imbalance as well as to regulate the DC link voltage a dual output boost converter with pulse delay control is proposed. The modeling, simulation and experiments show an improvement in the compensation voltage using pulse delay control compared to the previously proposed methods in the literature. The synchronous current control and the grid connection of the three-level converter have been accomplished in the laboratory.  Finally, the three-level power converter system has been tested with a linear permanent magnet generator at Lysekil to analyze the controller requirements.

Variable speed motor drives are being rapidly deployed for a vast range of applications in order to increase efficiency and to allow for a higher level of control over the system. One of the important areas within the field of variable speed motor drives is the system's operational boundary. Presently, the operational boundaries of variable speed motor drives are set based on the operational boundaries of single speed motors, i.e. by limiting current and power to rated values. This results in under-utilization of the system, and places the motor at risk of excessive power losses. The constant power loss (CPL) concept is introduced in this dissertation as the correct basis for setting and analyzing the operational boundary of variable speed motor drives. The control and dynamics of the permanent magnet synchronous motor (PMSM) drive operating with CPL are proposed and analyzed. An innovative implementation scheme of the proposed method is developed. It is shown that application of the CPL control system to existing systems results in faster dynamics and higher utilization of the system. The performance of a motor drive with different control strategies is analyzed and compared based on the CPL concept. Such knowledge allows for choosing the control strategy that optimizes a motor drive for a particular application. Derivations for maximum speed, maximum current requirements, maximum torque and other performance indices, are presented based on the CPL concept. High performance drives require linearity in torque control for the full range of operating speed. An analysis of concurrent flux weakening and linear torque control for PMSM is presented, and implementation strategies are developed for this purpose. Implementation strategies that compensate for the variation of machine parameters are also introduced. A new normalization technique is introduced that significantly simplifies the analysis and simulation of a PMSM drive's performance. The concepts presented in this dissertation can be applied to all other types of machines used in high performance applications. Experimental work in support of the key claims of this dissertation is provided. / Ph. D.

In recent years, combat aircraft with external stores have experienced a decrease in their mission capabilities due to lack of robustness of the current passive wing/store flutter suppression system to both structured as well as unstructured uncertainties. The research program proposed here is to investigate the feasibility of using a piezoceramic wafer actuator for active control of store flutter with the goal of producing a robust feedback system that demonstrates increased performance as well as robustness to modeling errors. This approach treats the actuator as an active soft-decoupling tie between the wing and store, thus isolating the wing from store pitch inertia effects. Advanced control techniques are used to assess the nominal performance and robustness of wing/store system to flutter critical uncertainties. NOTE: (10/2009) An updated copy of this ETD was added after there were patron reports of problems with the file. / Ph. D.

Meshed high-voltage direct current grids are becoming an increasingly important technology for integrating renewable energies into the power system. To control the grids in the best possible way, optimal converter and grid control strategies are needed. This project studies how a four-terminal high-voltage direct current grid is operated and controlled by implementing different grid and converter control strategies. The grid control strategies examined are centralized voltage control and distributed voltage control with and without deadband. Simulations are made in the software PSCAD. Different fault types on the grid are studied to investigate how the power flow and voltage level are affected. An optimal value for both the deadband width and droop constant has been identified. Moreover, the results indicate that centralized droop control is not a suitable grid control strategy, whereas distributed voltage control with and without deadband are. The fault study indicates no differences between distributed voltage control with and without deadband. The power flow and voltage levels are identical for all fault types. / Högspända likströmsnät spelar en allt större roll med att integrera förnyelsebar energi i våra elnät. För att styra dessa nät på bästa möjliga sätt krävs optimala omvandlar- och nätkontrollstrategier. I detta projekt studeras hur ett fyrterminalt högspänt likströmsnät kan styras och drivas genom att implementera olika omvandlar- och nätkontrollstrategier. De nätkontrollstrategier som studerats är centraliserad spänningskontroll och distribuerad spänningskontroll med och utan ett spänningsintervall. Alla simuleringar har utförts i programmet PSCAD. Olika fel i nätet har även studerats för att undersöka hur effektflödet och spänningsnivån påverkas. Ett optimalt värde på både spänningsintervallet och droop konstanten har identifierats. Dessutom har resultat som indikerar att centraliserad spänningskontroll inte är en lämplig nätkontrollstrategi erhållits, medan distribuerad spänningskontroll med och utan spänningsintervall är det. Felsimuleringarna påvisar ingen skillnad mellan distribuerad spänningskontroll med och utan spänningsintervall. Effektflödet och spänningsnivån är identiska för alla fel.

Friction force oscillations caused by changing properties of the contact zone between brake disc and pad are well known from various applications. Resulting effects like brake judder are known phenomena in brake technologies and in the scope of various scientific work. A new measure to potentially reduce brake torque oscillations is the active compensation with the use of the control system of a self-energizing hydraulic brake (SEHB). New in comparison to traditional disc brakes is the fact that the brake torque is measured by the pressure in an additional supporting cylinder. Thus, the brake system is able to work in brake torque control mode. Within this paper a dynamic simulation model of the SEHB is shown and evaluated with measurement data achieved from a full scale test rig for railway applications. Based on the simulation model a pressure control strategy is developed to minimize brake torque oscillations of lower frequencies. The control parameters of the simulation are transferred to the experimental setup. Finally, simulation and experimental results are compared. Future work will deal with the development of control strategies to additionally minimize brake torque oscillations of the higher dynamics.

To enhance test security of high stakes tests, it is vital to understand the way various exposure control strategies function under various IRT models. To that end the present dissertation focused on the performance of several exposure control strategies under the generalized partial credit model with an item pool of 100 and 200 items. These procedures are relatively easy to implement and have shown promise as an alternative to more complex exposure control strategies. Through unique algorithms these procedures select an item for administration from a subset of items in the item pool. The five procedures examined for efficacy were the modified within .10 logits, restricted modified within .10 logits, randomesque, restricted randomesque, and progressive restricted procedures. The modified within .10 logits, restricted modified within .10 logits, and randomesque, and restricted randomesque procedures select an item for administration from a subset of optimal items. To test the effect of the number of items available for selection in this subset, 3, 6, and 9 items were made available for selection in these procedures. Maximum information item selection was used as a base line, no exposure control, condition. The progressive restricted, restricted randomesque, and restricted modified within .10 logits procedures were found to optimally protect test security while not significantly degrading measurement precision. The restricted forms of the randomesque and modified within .10 logits procedures proved superior to their base procedures, particularly in controlling average maximum exposure rate. The incrementation of item group size in the modified within .10 logits, restricted modified within .10 logits, and randomesque, and restricted randomesque procedures demonstrated that increasing the item group size provided better test security while not significantly degrading measurement precision. Additionally, in general, the increase of the item pool size from 100 to 200 improved measurement precision and test security. Implications towards practical application are discussed and directions for future research are suggested. / text

Developmental transitions are experienced throughout the life-span and necessitate adapting to significant and unpredictable changes (Heckhausen et al., 2010; Perry, 2003). The shift from high school to university in young adulthood serves as an exemplar of how these challenging junctures can undermine motivation and well-being. Recent evidence suggests that most (85%) young adults making this transition feel overwhelmed, half (50%) experience immense anxiety (ACHA, 2012), and more than one quarter (28%) withdraw from their institutions by the end of their first year (Snyder & Dillow, 2013). The present dissertation was designed to counter these developments by conducting a systematic analysis of whether motivation-focused thinking (selective secondary control) sustained young adults’ goal striving, goal attainment, and well-being based on propositions stemming from the motivational theory of life-span development (Heckhausen et al., 2010). Study 1 comprised a seven-month field study and showed that motivation-focused selective secondary control striving positively predicted young adults use of behavior-focused selective primary control strategies, which in turn influenced academic performance. Study 2 was based on a seven-month field study and built on Study 1 by demonstrating that increasing selective secondary control striving was related to lower levels of depressive and stress-related physical symptoms for young adults with low high school grades. These effects were mediated by theoretically-derived mechanisms involving selective primary control and discrete emotions. Building on the preceding studies, Study 3 involved a seven-month, pre-post, field design and showed that students with low high school grades and high perceived control who received a motivation-enhancing selective secondary control treatment attained year-end course grades that were 8% higher than their no-treatment peers (74.85% vs. 66.68%). Consistent with theory, treatment effects were mediated by selective secondary and primary control strategies and emotions. Findings from these studies advance the literature by documenting previously unexplored antecedents, consequences, mediators, moderators, and manipulations (treatment) of selective secondary control for young adults in the midst of a challenging life course transition. / October 2016