A continued increase in government regulations for fuel economy and emissions has driven automakers and suppliers to take a large interest in hybridizing vehicles to help them achieve the new requirements. This increased vehicle electrification has resulted in unconventional vehicle cooling requirements. Electrified vehicle batteries and motors operate under different temperature regimes and cooling loads change drastically with driving styles and conditions. A variable-load cooling system was designed, implemented and tested on the Mississippi State University EcoCAR extended-range electric vehicle (E-REV). This system, utilizing variable flow pumps and variable speed fans, was shown to successfully cool the electronic components under the worst-case design conditions, while providing low energy consumption under normal conditions. When compared to a baseline system utilizing no variable duty cycle components, the variable cooling power system reduced energy consumption during testing both on-road at MSU’s facility and on-road at General Motors proving grounds in Michigan.

Feedback active noise control (ANC) has been applied as a means of attenuating broadband noise from a small axial cooling fan. Such fans are used to maintain thermal stability inside of computers, projectors, and other office equipment and home appliances. The type of low-level noise radiated from axial cooling fans has been classified as harmful to productivity and human well being. Previous research has successfully implemented feed-forward ANC, targeting specific narrow-band fan noise content related to the blade passage frequency (BPF) of the fan. The reference signal required for a feed-forward algorithm limits its ability to attenuate much of the noise content; however, it is also desirable to reduce broadband fan noise. Feedback control is a logical alternative in the absence of a valid reference signal. The fan used for this research was mounted in one of the six aluminum panels that constituted a mock computer case. The fan was surrounded by four miniature loudspeakers as control sources and four small electret microphones as error sensors. A feasibility study was conducted with a single channel of analog feedback control. However, for the majority of this research, the ANC algorithm was executed on a digital signal processor. Several electronic modules provided the necessary signal conditioning and conversion for the process. A method is proposed and validated for predicting the overall attenuation that can be obtained for a specific fan, based on its autocorrelation measurement. Studies were performed in order to determine the difference in performance between static and adaptive controllers. Comparisons are made between decentralized and centralized controllers, the results of which are presented in this thesis. Feedback ANC is demonstrated as a good alternative to feed-forward ANC for the reduction of BPF related tonal fan noise content. Some low-frequency broadband attenuation is achieved. The delay time associated with current DSP technology is shown to be too long to effectively attenuate flow noise (the main component of broadband fan noise). Adaptive control proved to be necessary for stability and performance in the feedback controller. Decentralized control is shown to outperform centralized control for this specific application.

Robots and other automated systems have potential use in many different fields. As the scope of robot applications that robots are used for increases, there is a growing desire to have human operators manage multiple robots. Typical methods of enabling operators to multi-task in this way involve some combination of user interfaces that support human cognition and advanced robot autonomy. Our research explores a complementary method of managing multiple robots by utilizing operator teams. The evidence suggests that for appropriate task scenarios, two cooperating operators can be more than twice as effective as one operator working alone.

The motivation for this research is the need to improve performance of the autonomous flight of a tailsitter UAV. Tailsitter aircraft combine the hovering and vertical take-off and landing capability of a rotorcraft with the long endurance flight capability of a fixed-wing aircraft. The particular aircraft used in this research is the V-Bat, a tailsitter UAV with a conventional wing and the propeller and control surfaces located within a ducted-fan tail assembly. This research focuses on identifying the models and parameters of the V-Bat in hover and level flight as a basis for the design of the control systems for hover, level, and transition modes of flight.Models and parameters were identified from experimental data. Wind-tunnel tests, bench tests, and flight tests were performed in a variety of flight conditions. Wind tunnel tests yielded force and moment coefficients over the full flight envelope of the V-Bat. Models and parameters for longitudinal, lateral, and hover flight are presented. Bench tests were conducted to enhance understanding about the ducted-fan propulsion system and the effectiveness of the control surfaces. The thrust characteristics of the ducted fan were measured. Control derivatives were derived from force and moment measurements. Flight tests were completed to obtain dynamic models of the V-Bat in hover flight. Using frequency-domain system identification methods, frequency-response and transfer function models of roll, pitch, and yaw responses to aileron, elevator, and rudder control input were derived.The results obtained from these experimental tests were used to identify models and parameters of the V-Bat aircraft, giving insight into its behavior and enhancing the control analysis and simulation capabilities for this aircraft, thus providing the increased levels of understanding needed for autonomous flight.

Distortion tolerant fans represent the enabling technology for the successful implementation of highly integrated airframe propulsion system vehicles. This investigation extends the study of fan-distortion interactions to an actual turbofan engine with a total pressure distortion profile representative of a boundary-layer ingesting (BLI) embedded engine. The goal was to make a series of flow measurements that contribute to the overall physical understanding of this complex flow situation. Proper uncertainty analysis is critical to extracting meaning from the data measured in this study. The important information in the measurements is contained in small differences that lead to large impacts on the fan performance. In some cases, these differences were measured to a useful degree of accuracy, while in others they were not. One important application of the uncertainty analysis techniques developed in this work is the identification of the dominant error sources that resulted in unacceptable uncertainties. This dissertation presents an experimental study of transonic fan response to inlet total pressure distortion. A Pratt and Whitney JT15D-1 turbofan engine was subjected to a total pressure distortion representative of a boundary layer ingesting serpentine inlet. A 5-hole probe measured the aerodynamic response of the fan rotor in terms of flow angles, total pressure, and static pressure. A thermocouple embedded in the probe measured the rotor outlet total temperature. These measurements enabled the full characterization of the flow condition at each measurement point. The results indicate that a trailing edge separation and reattachment cycle experienced by the blades caused variations in the work input to the flow and resulted in a non-uniform rotor outlet flow profile. The details of the aerodynamic process and several means for improving distortion response are presented in this context. As a second theme, the modern measurement and uncertainty analysis techniques required to obtain useful information in this situation are developed and explored. Uncertainty analysis is often treated as a less glamorous afterthought in experimental research. However, as technology develops along lines of ever increasing system-level integration, simply suggesting the solution to a single flow situation does not repre- sent closure to the larger problem. In addition to frameworks for developing distortion tolerant fans, frameworks for developing frameworks are required. Uncertainty-drivenexperimental techniques represent the enabling methodology for the discovery and un- derstanding of the subtle phenomena associated with such coupled performance. These considerations are required to extend the usefulness of the results to the overarching issue of integrating the complex performance of individual components into an overall superior system. The experimental methods and uncertainty analysis developed in this study are presented in this context. / Ph. D.

A new method for predicting forced vibratory blade response to total pressure distortion has been developed using modal and harmonic analysis. Total pressure distortions occur in gas turbine engines when the incoming airflow is partially blocked or disturbed. Distorted inlet conditions can have varying effects on engine performance and engine life. Short-term effects are often in the form of performance degradation where the distorted airflow causes a loss in pressure rise, and a reduction in mass flow and stall margin. Long-term effects are a result of vibratory blade response that can ultimately lead to high cycle fatigue (HCF), which in turn can quickly cause partial damage to a single blade or complete destruction of an entire compressor blade row, leading to catastrophic failure of the gas turbine engine. A better understanding and prediction of vibratory blade response is critical to extending engine life and reducing HCF-induced engine failures. This work covers the use of finite element modeling coupled with computational fluid dynamics-generated pressure fields to create a generalized forcing function. The first three modes of a low-aspect-ratio, transonic, first stage blade of a two-stage fan were examined. The generalized forcing function was decomposed to the frequency domain to identify the dominant harmonic magnitude present, as well as other contributing harmonics. An attempt to define the relationship between modal force with varying total pressure distortion levels produced a sensitivity factor that describes the relationship in the form of a simple multiplier. A generalized force was applied to the blade and varied harmonically across a frequency range known to contain the first natural frequency. The mean rotor stress variation was recorded and compared to experimental results to validate the accuracy of the model and verify its ability to predict vibratory blade response accurately. / Master of Science

The rising interest in fan performance in the presence of total pressure distortion, a topic of fundamental interest for integrated airframe/engine architectures, has led to increased research in ground based testing environments. Included in these studies is the generation of simulated total pressure distortion profiles using wire mesh screens. Although the inlet duct development of total pressure distortion patterns has been studied in a historical context when distortion effects on engine performance were first of interest, these were typically simplified experimental studies for low-speed flows. To aid in the understanding of total pressure distortion development approaching a transonic fan face, a series of experiments were conducted to detail the development of such a profile downstream of the screen plane in the absence and presence of fan effects. Presented is an extensive experimental set to detail (1) the evolution of a screen-generated total pressure distortion profile as it develops in a constant diameter inlet duct and (2) the effect that a single stage transonic fan has on the distortion development. Included is a detailed analysis of the distortion profile characteristics for increasing development length, and the behavioral changes of the profile when fan blockage is present near the screen plane. Recommendations are made regarding the placement of total pressure distortion screens relative to the fan face, and insights are given into the expected profile evolution. This work is a contributing part of an ongoing systematic investigation of fan performance when subjected to screen-generated total pressure inlet distortion. / Master of Science

A flex-fan has flexible blades which undergo large deformation under centrifugal forces to give the desired air-flow and power-consumption characteristics with speed. The finite element technique has been used to obtain the deflected shape of the blade of such a fan used for automobile radiator cooling. The natural frequencies of vibration are also evaluated at different speeds, up to 5,000 rpm. A partially conforming deflection function has been used in the analysis. The blade has been treated as a thin shell, idealized as an assembly of thin flat triangular elements. / Thesis / Master of Engineering (ME)

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