Browsing by Subject "Control"

Now showing 1 - 20 of 38
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    Controller Design and Analysis of Dual-stage Hard Disk Drives in the Presence of Micro-Actuator Stroke Limitation
    (2022-11) Chakraborty, Manash
    With the continuous increase in storage capacity, the width of a hard disk drive (HDD) data track is decreasing, and the traditional single-stage actuation system is insufficient for such high-precision actuation. Hence, a secondary high-bandwidth piezoelectric (PZT) type micro-actuator is widely used to enhance HDD's precision servo tracking capability. However, the micro-actuator is typically prone to actuator saturation, which limits the achievable closed-loop sensitivity performance of a controller design. Hence, any undesired high-magnitude disturbance might cause an aggressive controller to demand high stroke usage from the actuator system, which can lead to saturation of the micro-actuator. This work presents an analysis method to predict the micro-actuator stroke usage for a given controller by taking advantage of the stochastic interpretation of H2 system norm. Measured data from a Seagate HDD are used to model several disturbance environments and calibrate the proposed prediction model. Then the idea of predicting the micro-actuator stroke usage is used to explore a mixed H2/H-infinity controller synthesis method to avoid saturation of the micro-actuator in a dual-stage actuator system while maximizing the closed-loop disturbance rejection performance. Finally, a two-step nonlinear analysis method is also discussed to determine the worst-case disturbance rejection performance under micro-actuator saturation by utilizing the concept of bounded nonlinearity. Necessary mathematical proofs are provided to support the proposed analysis method and a numerical example is discussed with a validation process via numerical simulation.
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    Data for Open water dreissenid mussel control projects: lessons learned from a retrospective analysis
    (2022-08-15) Dahlberg, Angelique, D.; Waller, Diane, L.; Hammond, David; Lund, Keegan; Phelps, Nicholas, B. D.; edge0023@umn.edu; Dahlberg, Angelique, D.; Minnesota Aquatic Invasive Species Research Center, University of Minnesota
    Dreissenid mussels are one of the most problematic aquatic invasive species (AIS) in North America, causing significant ecological and economic impacts in waterbodies where established. To date, dreissenid mussel control efforts in open water have included physical, biological, and chemical methods. The feasibility of successfully managing or even eradicating dreissenid mussels in lakes is relatively undocumented and unstudied in freshwater management literature. Additionally, control efforts are sometimes stymied by perceptions that the impacts to nontarget species will be unacceptable. The published literature evaluating both these two aspects is limited. Here, we present information on 33 open water dreissenid mussel control projects in 23 lakes across North America. Projects were categorized as rapid response eradication (n=16), established population eradication (n=8), suppression (n=3), or research (n=6).
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    Design and analysis of optimal ascent trajectories for stratospheric airships
    (2013-08) Mueller, Joseph Bernard
    Stratospheric airships are lighter-than-air vehicles that have the potential to provide a long-duration airborne presence at altitudes of 18-22 km. Designed to operate on solar power in the calm portion of the lower stratosphere and above all regulated air traffic and cloud cover, these vehicles represent an emerging platform that resides between conventional aircraft and satellites. A particular challenge for airship operation is the planning of ascent trajectories, as the slow moving vehicle must traverse the high wind region of the jet stream. Due to large changes in wind speed and direction across altitude and the susceptibility of airship motion to wind, the trajectory must be carefully planned, preferably optimized, in order to ensure that the desired station be reached within acceptable performance bounds of flight time and energy consumption. This thesis develops optimal ascent trajectories for stratospheric airships, examines the structure and sensitivity of these solutions, and presents a strategy for onboard guidance. Optimal ascent trajectories are developed that utilize wind energy to achieve minimum-time and minimum-energy flights. The airship is represented by a three-dimensional point mass model, and the equations of motion include aerodynamic lift and drag, vectored thrust, added mass effects, and accelerations due to mass flow rate, wind rates, and Earth rotation. A representative wind profile is developed based on historical meteorological data and measurements. Trajectory optimization is performed by first defining an optimal control problem with both terminal and path constraints, then using direct transcription to develop an approximate nonlinear parameter optimization problem of finite dimension. Optimal ascent trajectories are determined using SNOPT for a variety of upwind, downwind, and crosswind launch locations. Results of extensive optimization solutions illustrate definitive patterns in the ascent path for minimum time flights across varying launch locations, and show that significant energy savings can be realized with minimum-energy flights, compared to minimum-time time flights, given small increases in flight time. The performance of the optimal trajectories are then studied with respect to solar energy production during ascent, as well as sensitivity of the solutions to small changes in drag coefficient and wind model parameters. Results of solar power model simulations indicate that solar energy is sufficient to power ascent flights, but that significant energy loss can occur for certain types of trajectories. Sensitivity to the drag and wind model is approximated through numerical simulations, showing that optimal solutions change gradually with respect to changing wind and drag parameters and providing deeper insight into the characteristics of optimal airship flights. Finally, alternative methods are developed to generate near-optimal ascent trajectories in a manner suitable for onboard implementation. The structures and characteristics of previously developed minimum-time and minimum-energy ascent trajectories are used to construct simplified trajectory models, which are efficiently solved in a smaller numerical optimization problem. Comparison of these alternative solutions to the original SNOPT solutions show excellent agreement, suggesting the alternate formulations are an effective means to develop near-optimal solutions in an onboard setting.
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    Efficient Propulsion for Versatile Unmanned Aerial Vehicles: Studies in Mechanics and Control
    (2021-02) Henderson, Travis
    This thesis presents a control algorithm for significantly enhancing the available thrust and minimizing the required electrical power consumption of a Variable-Pitch Propulsion (VPP) system, where the VPP system is made up of a brushless DC motor and a variable-collective-pitch propeller with its own servo motor. The variable-collective-pitch propeller mechanism has received recent attention because of the mechanism’s capability to enhance thrust response bandwidth and propulsive efficiency compared to conventional Unmanned Aerial Vehicle (UAV) propulsion systems with rigid-geometry propellers; the mechanism has this capability due to a second mechanical degree of freedom in the propeller geometry, allowing the collective pitch angle of the propeller blades to vary according to actuation from a servo motor. When paired with a properly designed control algorithm, the motor speed and pitch angle can be tuned in real time to track prescribed thrust trajectories while satisfying some optimality condition. Motivation for research into highly efficient VPP propulsion systems is encouraged by the intense interest from private and public sectors in UAVs that are capable of Vertical TakeOff and Landing (VTOL); while generally capable of both fixed-wing and hovering flight, VTOL UAVs with rigid-geometry propellers often exhibit short flight time due to non-optimal propulsion system efficiency across-the-board. Prior research into power-minimizing control strategies for small VPP systems has been targeted at multi-rotor platforms and has thus made assumptions that limit variation in the speed of propeller inflow and in the magnitude of thrust, thus limiting the technology’s applicability to VTOL platforms. The control algorithm presented in this thesis is designed to accommodate for the wide range of air inflow speeds and thrust magnitudes through the following algorithm components: a linear feedback thrust controller with a nonlinear, adaptive feedforward thrust model derived from Blade Element Momentum propeller theory; an estimator to tune the thrust feedforward model parameters in real-time; and an Extremum Seeking algorithm for tracking the minimum-power control input configuration. Analysis of controller performance is discussed with reference to simulated and physical validation experiments.
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    Evaluation of immune management strategies to control and eliminate porcine reproductive and respiratory syndrome virus (PRRSv)
    (2013-02) Linhares, Daniel Correia Lima
    Porcine reproductive and respiratory syndrome (PRRS) is an infectious disease caused by PRRS virus (PRRSv). PRRSv is considered one of the most economically important infectious agents in the swine industry worldwide. This thesis evaluated immune management strategies to eliminate PRRSv from breeding herds, assessed the impact of those strategies in production losses, evaluated management risk factors associated with successful PRRSv elimination or failure, and lastly evaluated vaccination as means to reduce virus dissemination from infected growing pig populations. Chapter 2 compared the use of two immunogens as part of load-close-expose programs in regards to the time it takes to reach PRRSv stability (TTS) from infected breeding herds. Results showed that despite the great variability of TTS between enrolled herds, there were some variables associated with shorter TTS. Specifically, herds that used LVI as the method of whole-herd exposure reached TTS earlier than herds that used MLV vaccines. Moreover, herds with history of PRRSv infection in the 3 years prior to our study reached TTS sooner than herds without history of PRRSv in those same 3 years. Furthermore, herds assisted by a specific veterinary clinic reached TTS sooner than all other herds suggesting that there might be management practices associated with shorter TTS. Our results also showed that PRRSv-monitoring must be done repeatedly over time to increase confidence of PRRSv-negative status of weaned piglets. Altogether, those findings represent prove of concept that herds can reach PRRSv stability as soon as 84 days from establishment of LCE. Further studies are needed to better understand specific factors associated with reaching short TTS, such as farm layout, pig flow and implementation of specific management practices during the period of herd closure. Chapter 3 evaluated the effect of attenuated PRRSv vaccine inoculation compared to the use of live-virulent virus inoculation on production performance in breeding herds. It was shown that herds that used MLV vaccine as part of load-close-expose herd closure programs recovered production levels and had a less severe production impact than herds that used LVI. Also, herds that reported previous PRRSv infection reached time to baseline production (TTBP) sooner than herds with no history of PRRSv infection in the previous 3 years. Interestingly, herds assisted by a specific veterinary clinic recovered production faster than other herds, raising the hypothesis that specific management practices could be associated with herd closure effectiveness. The chapter 3 addendum consisted of economic models to assist veterinarians to make informed decisions between LVI and MLV as part of LCE program to eliminate PRRSv. Taking in consideration the future prices for market hogs and pig feed of the next 12 months, and $13.52 loss per pig that is PRRSv-positive, the results suggested that MLV would be a better economical choice. Chapter 4 was a follow-up from the previous 2 chapters and investigated herd-closure practices associated with successful PRRSv-elimination from breeding herds. It showed that the success rate of LCE programs was 76% and 92% for LVI and MLV herds, when failures associated with unrelated PRRSv were excluded from the analysis although these differences were not statistically significant. Moreover, one out of six herds that achieved 90 days of failure to detect PRRSv in due to wean piglets failed to achieve AASV category III, which indicates that more strict monitoring programs should be adopted in herds undergoing PRRSv elimination. Interestingly, herds assisted by different veterinary clinics had different set of recommendations of management practices to be followed during LCE, indicating that there was no agreement between veterinarians on what is the relative importance of each management practice evaluated. The variables associated with failure to reach AASV category III were a) being infected with a PRRSv of RFLP pattern 1-4-4 and b) holding back pigs at weaning for quality. Chapter 5 focused on PRRSv-infected growing pig populations. Growing pig populations are a major source of PRRSv dissemination within regions. The effect of an attenuated PRRSv vaccine was evaluated on shedding and generation of aerosols of a wild-type virus from an infected growing pig population raised under Minnesota's swine industry field conditions. Our results showed that vaccinating acutely PRRSv infected growing pigs with MLV vaccine reduced duration and magnitude of PRRSv detection in aerosols exhausted from the pig barn. Further studies are needed to characterize the effect of implementation (rather than recommendation) of key management practices on the success of PRRSv elimination programs. There is also a need to better understand the procedures to prepare live (virulent) virus inoculum to expose adult animals in load-close-expose programs. For instance, there is a need to document the effect of PRRSv infectivity dose, route of exposure and materials used to dilute the serum on TTS and TTBP. On the growing pig side, there is a need to validate other effective methods to decrease virus dissemination from infected pig sites that continue to pose a risk for neighboring pig populations, for example by inactivating PRRSv in aerosols coming out of infected pig barns. Altogether, the work presented in this thesis provided science-based information on immune management strategies to control and eliminate PRRSv infection from pig populations. Information herein reviewed, discovered, described and discussed has direct implications to the swine industry and can assist veterinarians to choose appropriate strategies to reduce production losses and decrease PRRSv dissemination from infected pig populations.
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    FASER Flight 02
    (2011-09-08) Taylor, Brian
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    FASER Flight 05
    (2014-07-28) Taylor, Brian
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    FASER Flight 05 v2
    (2014-07-29) Taylor, Brian
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    FASER Flight 06
    (2014-07-28) Taylor, Brian
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    FASER Flight 06 v2
    (2014-07-29) Taylor, Brian
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    FASER Flight 07
    (2014-07-28) Taylor, Brian
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    FASER Flight 07 v2
    (2014-07-29) Taylor, Brian
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    FASER Flight 08
    (2014-07-28) Taylor, Brian
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    FASER Flight 08 v2
    (2014-07-29) Taylor, Brian
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    FASER Flight 09
    (2014-07-28) Taylor, Brian
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    FASER Flight 09 v2
    (2014-07-29) Taylor, Brian
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    Goldy Flight Control System v1.0
    (2014-07-23) Johnson, Will
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    HIFU Monitoring and control With dual-mode ultrasound arrays
    (2013-11) Casper, Andrew Jacob
    The biological effects of high-intensity focused ultrasound (HIFU) have been known and studied for decades. HIFU has been shown capable of treating a wide variety of diseases and disorders. However, despite its demonstrated potential, HIFU has been slow to gain clinical acceptance. This is due, in part, to the difficulty associated with robustly monitoring and controlling the delivery of the HIFU energy. The non-invasive nature of the surgery makes the assessment of treatment progression difficult, leading to long treatment times and a significant risk of under treatment. This thesis research develops new techniques and systems for robustly monitoring HIFU therapies for the safe and efficacious delivery of the intended treatment. Systems and algorithms were developed for the two most common modes of HIFU delivery systems: single-element and phased array applicators. Delivering HIFU with a single element transducer is a widely used technique in HIFU therapies. The simplicity of a single element offers many benefits in terms of cost and overall system complexity. Typical monitoring schemes rely on an external device (e.g. diagnostic ultrasound or MRI) to assess the progression of therapy. The research presented in this thesis explores using the same element to both deliver and monitor the HIFU therapy. The use of a dual-mode ultrasound transducer (DMUT) required the development of an FPGA based single-channel arbitrary waveform generator and high-speed data acquisition unit. Data collected from initial uncontrolled ablations led to the development of monitoring and control algorithms which were implemented directly on the FPGA. Close integration between the data acquisition and arbitrary waveform units allowed for fast, low latency control over the ablation process. Results are presented that demonstrate control of HIFU therapies over a broad range of intensities and in multiple in vitro tissues. The second area of investigation expands the DMUT research to an ultrasound phased-array. The phased-array allows for electronic steering of the HIFU focus and imaging of the acoustic medium. Investigating the dual-mode ultrasound array (DMUA) required the design and construction of a novel ultrasound-guided focused ultrasound (USgFUS) platform. The platform consisted of custom hardware designed for the unique requirements of operating a phased-array in both therapeutic and imaging modes. The platform also required the development of FPGA based signal processing and GPU based beamforming algorithms for online monitoring of the therapy process. The results presented in this thesis represent the first demonstration of a real-time USgFUS platform based around a DMUA. Experimental imaging and therapy results from series of animal experiments, including a 12 animal GLP study, are presented. In addition, in vitro control results, which build upon the DMUT work, are presented.
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    Improving Traffic Signal Operations for Integrated Corridor Management
    (Minnesota Department of Transportation, 2013-07) Liu, Henry X.; Hu, Heng
    The Integrated Corridor Management (ICM) approach has drawn increasingly more attention in recent years because it is believed to be a promising tool to mitigate urban traffic congestion. In this project, a maximum flow based control model was first developed to handle oversaturated traffic conditions at signalized arterials. Based on the arterial control model, an integrated control model was proposed to manage network congestion. Through diversion control, the model aims to fully utilize the available capacity along parallel routes. The impact of the diversion traffic is considered, especially for signalized arterials, so that traffic congestion on the diversion route can be reduced or eliminated by proper adjustment of signal timings. This model does not rely on time-dependent traffic demand as model inputs and it is ready to be implemented at typical parallel traffic corridors where the standard detection system is available. The performance of the proposed model was tested using microscopic traffic simulation in the I-394 and TH 55 corridor in Minneapolis, Minnesota. The results indicate that the proposed model can significantly reduce network congestion.