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Title: Control of hybrid dynamics with application to a hopping robot
Creator: Mathis, Frank Benton
Date: 2016
Collection: Electronic Theses & Dissertations
Description: "Control of dynamic motion is an important subject of study in robotics as it is desirable for robots to have a specific motion pattern rather then moving to a set point. The motions of robots also involve changing dynamic behaviors due to interaction with the environment, such as during contact, and this leads to hybrid system dynamics. A popular example of a hybrid dynamical system is a legged robot; the hybrid dynamics is due to the periodic switching of swing and stance legs and impulsive...
Show more"Control of dynamic motion is an important subject of study in robotics as it is desirable for robots to have a specific motion pattern rather then moving to a set point. The motions of robots also involve changing dynamic behaviors due to interaction with the environment, such as during contact, and this leads to hybrid system dynamics. A popular example of a hybrid dynamical system is a legged robot; the hybrid dynamics is due to the periodic switching of swing and stance legs and impulsive dynamics due to ground contacts. Legged robots require control of a dynamic trajectory defined by the walking gait or running motion. For legged robots, the spring loaded inverted pendulum (SLIP) model is commonly used to describe the dynamic motion in a simplified manner. The SLIP model has also been used for control of hopping robots and a fundamental limitation of the model is that it fails to account for impact with the ground; this is due to its single degree-of-freedom in the vertical direction. We investigate the control of a hopping robot starting from a more general two-mass model and then expand the theory to planar multi-link robot systems. The investigation involves two ground contact models, rigid and elastic, for the objective of apex height control. In the rigid case, the ground is assumed to provide an impulsive force to the hopping robot resulting in an inelastic collision. A hybrid control strategy is designed to deal with the hybrid dynamical system: a continuous controller based on partial feedback linearization is used in conjunction with a discrete controller that updates a control parameter at each hop to achieve the control objective. In the elastic case, the ground acts as a massless spring, which deflects as the robot exerts a force upon contact. In this case, we show that a continuous controller based on the backstepping algorithm can ensure asymptotic convergence to the desired apex height. Several robot configurations are considered, and for each configuration the complete hybrid dynamics is taken into account while designing the controller. The controllers compensate for the impulsive dynamics as well as higher order dynamics that are ignored in simplified models such as the SLIP model. Experimental validation of apex height control of a two-mass hopping robot on a rigid foundation is provided"--Pages ii-iii.
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Title: Reliability improvement of DFIG-based wind energy conversion systems by real time control
Creator: Elhmoud, Lina Adnan Abdullah
Date: 2015
Collection: Electronic Theses & Dissertations
Description: Reliability is the probability that a system or component will satisfactorily perform its intended function under given operating conditions. The average time of satisfactory operation of a system is called the mean time between failures (MTBF) and. the higher value of MTBF indicates higher reliability and vice versa. Nowadays, reliability is of greater concern than in the past especially for offshore wind turbines since the access to these installations in case of failures is both costly and...
Show moreReliability is the probability that a system or component will satisfactorily perform its intended function under given operating conditions. The average time of satisfactory operation of a system is called the mean time between failures (MTBF) and. the higher value of MTBF indicates higher reliability and vice versa. Nowadays, reliability is of greater concern than in the past especially for offshore wind turbines since the access to these installations in case of failures is both costly and difficult. Power semiconductor devices are often ranked as the most vulnerable components from reliability perspective in a power conversion system. The lifetime prediction of power modules based on mission profile is an important issue. Furthermore, lifetime modeling of future large wind turbines is needed in order to make reliability predictions in the early design phase. By conducting reliability prediction in the design phase a manufacture can ensure that the new wind turbines will operate within designed reliability metrics such as lifetime.This work presents reliability analysis of power electronic converters for wind energy conversion systems (WECS) based on semiconductor power losses. A real time control scheme is proposed to maximize the system's lifetime and the accumulated energy produced over the lifetime. It has been verified through the reliability model that a low-pass-filter-based control can effectively increase the MTBF and lifetime of the power modules. The fundamental cause to achieve higher MTBF lies in the reduction of the number of thermal cycles.The key element in a power conversion system is the power semiconductor device, which operates as a power switch. The improvement in power semiconductor devices is the critical driving force behind the improved performance, efficiency, reduced size and weight of power conversion systems. As the power density and switching frequency increase, thermal analysis of power electronic system becomes imperative. The analysis provides information on semiconductor device rating, reliability, and lifetime calculation. The power throughput of the state-of-the-art WECS that is equipped with maximum power point control algorithms is subjected to wind speed fluctuations, which may cause significant thermal cycling of the IGBT in power converter and in turn lead to reduction in lifetime. To address this reliability issue, a real-time control scheme based on the reliability model of the system is proposed. In this work a doubly fed induction generator is utilized as a demonstration system to prove the effectiveness of the proposed method. Average model of three-phase converter has been adopted for thermal modeling and lifetime estimation. A low-pass-filter based control law is utilized to modify the power command from conventional WECS control output. The resultant reliability performance of the system has been significantly improved as evidenced by the simulation results.
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Title: Design considerations and estimated on-vehicle performance for a compression-couple based thermoelectric generator
Creator: Mansouri Boroujeni, Nariman
Date: 2015
Collection: Electronic Theses & Dissertations
Description: Approximately 55% percent of the energy produced from conventional vehicle resources is lost in the form of heat. An efficient waste heat recovery process will undoubtedly lead to improved fuel efficiency, reduced greenhouse gas emissions and increased profit. Thermoelectric generators (TEGs) are one of the most viable waste heat recovery approaches that are being widely studied among energy-intensive industries which focus on the ways to convert waste heat energy to electrical energy. With...
Show moreApproximately 55% percent of the energy produced from conventional vehicle resources is lost in the form of heat. An efficient waste heat recovery process will undoubtedly lead to improved fuel efficiency, reduced greenhouse gas emissions and increased profit. Thermoelectric generators (TEGs) are one of the most viable waste heat recovery approaches that are being widely studied among energy-intensive industries which focus on the ways to convert waste heat energy to electrical energy. With the rising cost of fuel and increasing demand for clean energy, solid-state thermoelectric (TE) devices are good candidates to reduce fuel consumption and CO2 emissions in an automobile. Although they are reliable energy converters, there are several barriers that have limited their implementation into wide market acceptance for automotive applications. These barriers include: the unsuitability of conventional thermoelectric materials for the automotive waste heat recovery temperature range; the rarity and toxicity of some otherwise suitable materials; and the limited ability to mass-manufacture thermoelectric devices from certain materials. However, skutterudite is one class of material that has demonstrated significant promise in the transportation waste heat recovery temperature domain. These materials have little toxicity, relatively abundant, and have been studied and developed by NASA-JPL and others for the past 20 years.The converted electrical energy can be used to recharge batteries, run auxiliary electrical accessories, support heating system, and etc. However, durability and reliability of the thermoelectric generators are the most significant concerns in the product development process. Cracking of the skutterudite materials at hot-side interface is found to be a major failure mechanism of thermoelectric generators under thermal cyclic loading. Cracking affects not only the structural integrity but also the energy conversion and overall performance of the system. In this project, cracking of thermoelectric material as observed in performance testing is analyzed using numerical simulations and analytic experiments. With the help of finite element analysis, the detailed distribution of stress, strain, and temperature are obtained for each design. Finite element based simulations show the tensile stresses as the main reason causing radial and circumferential cracks in the skutterudite. For thermoelectric generator design, loading conditions, closed-form analytical solutions of stress/strain distributions are derived and scenarios with minimum tensile stresses are sought. All these approaches yield a minimum stress/strain necessary to produce any cracks. Finally, based on FE and computational fluid dynamic (CFD) analysis, strategies in tensile stress reduction and failure prevention are proposed followed by the reasons to change the thermoelectric couple design for having a reliable thermoelectric generator.Using a modified compression couple technology, a 15-watt thermoelectric generator prototype was designed, built and tested. Experimental results of the TEG are presented. This prototype was analyzed using 1-D engine simulation and computational fluid dynamics (CFD), and the resulting analysis is presented. In a model configuration utilizing eight of these 15-watt TEGs, each having a 4% conversion efficiency, an estimated 136 watts of electricity could be produced at an operating point of 2000 RPM and 3 bar engine load in a 4.7L V6 gasoline engine.
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Title: Reaction-based modeling and control of an electrically boosted diesel engine
Creator: Men, Yifan
Date: 2019
Collection: Electronic Theses & Dissertations
Description: This dissertation presents the reaction-based modeling of diesel combustion and model-based control of diesel engine air path.The dissertation first presents a control-oriented reaction-based diesel combustion model that predicts the time-based rate of combustion, in-cylinder gas temperature and pressure over one engine cycle. The model, based on the assumption of a homogeneous thermodynamic combustion process, utilizes a two-step chemical reaction mechanism that consists of six species:...
Show moreThis dissertation presents the reaction-based modeling of diesel combustion and model-based control of diesel engine air path.The dissertation first presents a control-oriented reaction-based diesel combustion model that predicts the time-based rate of combustion, in-cylinder gas temperature and pressure over one engine cycle. The model, based on the assumption of a homogeneous thermodynamic combustion process, utilizes a two-step chemical reaction mechanism that consists of six species: diesel fuel (C10.8H18.7), oxygen (O2), carbon dioxide (CO2), water (H2O), nitrogen (N2), and carbon monoxide (CO). The temperature variation rate is calculated based on the rate of change of species concentrations, and the heat loss correlation is also used to study the model performance. The accuracy of the model is evaluated using the test data from a production GM 6.6 L, 8-cylinder, turbocharged engine. The model is calibrated over large engine speed and load range as well as different injection timings and exhaust gas recirculation (EGR) rates by solving the optimization problem. The calibrated reaction-based model accurately predicts the indicated mean effective pressure, while keeping the errors of in-cylinder pressure and temperature small, and at the same time, significantly reduces the calibration effort, especially when the engine is operated under multiple fuel injection operations, comparing to Wiebe-based combustion models. The calibrated model parameters have a strong correlation to engine speed, load and injection timings, and as a result, a universal parameter calibration structure is proposed for entire operational conditions.The second part of the dissertation is to obtain a parametric understanding of diesel combustion by developing a physics-based model that is able to predict the combustion metrics, such as in-cylinder pressure, burn rate, and indicated mean effective pressure (IMEP) accurately, over a wide range of operating conditions, especially with multiple injections. In the proposed model, it is assumed that the engine cylinder is divided into three zones: a fuel zone, a reaction zone, and an unmixed zone. The formulation of reaction and unmixed zones is based on the reaction-based modeling methodology, where the interaction between them is governed by Fick's law of diffusion. The fuel zone is formulated as a virtual zone, which only accounts for mass and heat transfer associated with fuel injection and evaporation. The model is validated using test data under different speed and load conditions, with multiple fuel injections and EGR. It is shown that the three-zone model outperformed the single-zone model in in-cylinder pressure prediction and calibration effort with a mild penalty in computational time. One set of calibration parameters are used for all engine operating conditions.The third part of the dissertation is modeling and control of engine air path with an electrically assisted boosting system. A physics-based control-oriented engine air path model with electrical assistance has been developed. The model is validated with steady-state engine test data and standard driving cycle data. Through one-dimensional simulation, it is found that the electrically assisted boosting system is able to improve engine performance under both steady-state and transient conditions. A model-based controller has been developed for the electric booster (eBoost) and bypass valve to improve the transient performance of engine load response. Experiments have been performed on a Ford 6.7 L, 8-cylinder, turbocharged diesel engine equipped with a prototype eBoost and a standard EGR valve as the bypass valve. Steady-state test results have shown that eBoost is capable of improving engine efficiency by reducing pumping loss, due to reduced turbine speed when eBoost is providing additional boost energy. In the transient process, eBoost is able to significantly reduce the response time of boost pressure tracking, as validated by load step tests.
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Title: Accurate torque pulsation estimation and reduction of ipmsms valid for any operating point and current waveform
Creator: Ruekamnuaychok, Tiraruek
Date: 2019
Collection: Electronic Theses & Dissertations
Description: In this thesis, a method to estimate the torque pulsation of IPMSMs is proposed. The method is based on an analytical torque equation of IPMSMs derived by using the concepts of energy and co-energy of a magnetic circuit. This method is valid and accurate for any operating point, including that under heavy magnetic saturation, and for any arbitrary current waveform. Also, by using the proposed equation, a method to reduce the torque pulsation is proposed. Simulation and experimental results...
Show moreIn this thesis, a method to estimate the torque pulsation of IPMSMs is proposed. The method is based on an analytical torque equation of IPMSMs derived by using the concepts of energy and co-energy of a magnetic circuit. This method is valid and accurate for any operating point, including that under heavy magnetic saturation, and for any arbitrary current waveform. Also, by using the proposed equation, a method to reduce the torque pulsation is proposed. Simulation and experimental results show that the proposed methods, for both estimation and reduction, are valid, accurate and effective.
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Title: The design, development, fabrication and testing of a 100 watt skutterudite thermoelectric generator
Creator: Lyle, Matthew
Date: 2011
Collection: Electronic Theses & Dissertations
Description: Thermoelectric technology is a method of renewable, alternative energy that utilizes the Seebeck effect to convert some of the thermal energy in a temperature gradient to electricity. The optimal temperature range for skutterudite thermoelectric devices is around 650°C, making them ideal for high temperature applications. At this temperature range, the skutterudite thermoelectrics have a device-level conversion efficiency of about 9%. As these devices are still in the development stage,...
Show moreThermoelectric technology is a method of renewable, alternative energy that utilizes the Seebeck effect to convert some of the thermal energy in a temperature gradient to electricity. The optimal temperature range for skutterudite thermoelectric devices is around 650°C, making them ideal for high temperature applications. At this temperature range, the skutterudite thermoelectrics have a device-level conversion efficiency of about 9%. As these devices are still in the development stage, testing that simulates real-world conditions is necessary to assess the feasibility of implementing skutterudite thermoelectric technology with current processes. A standardized procedure to test the skutterudite thermoelectric devices has been established to reduce variability in device fabrication and generator assembly. This procedure includes a measurement and tracking system to aid in establishing relationships between component properties and thermoelectric performance. In addition, a technology has been developed to electrically bypass any failed devices to preserve overall power generation.Results indicate that additional efforts are needed to address the high level of thermal stresses the devices experience during operation. Several methods to reduce thermal stresses and investigate potential stressors are proposed. In addition, the successful performance of the electrical bypass technology suggests that it is indeed a viable method of bypassing individual devices for experimental tests. Additional testing and improvements can be made as necessary to implement this technology in the envisioned 1 kW skutterudite thermoelectric generator.
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Title: Dynamic balance of a single cylinder reciprocating engine with optical access
Creator: Ruckle, Trevor W.
Date: 2014
Collection: Electronic Theses & Dissertations
Description: DYNAMIC BALANCE OF A SINGLE CYLINDER RECIPROCATING ENGINE WITH OPTICAL ACCESSByTrevor W. RuckleThe balance within reciprocating engines has always been a concern of engine designers. Any unbalance within an engine can result in component fatigue and failure, excessive vibration, and radiated noise (airborne and structural). When an engine is created with optical access, a Bowditch piston is placed on top a standard piston. This results in the reciprocating mass being significantly greater,...
Show moreDYNAMIC BALANCE OF A SINGLE CYLINDER RECIPROCATING ENGINE WITH OPTICAL ACCESSByTrevor W. RuckleThe balance within reciprocating engines has always been a concern of engine designers. Any unbalance within an engine can result in component fatigue and failure, excessive vibration, and radiated noise (airborne and structural). When an engine is created with optical access, a Bowditch piston is placed on top a standard piston. This results in the reciprocating mass being significantly greater, and it greatly increases the reciprocating force. The components that affect the balance of the engine were identified and different design aspects within each component that affect the balance were explored. The calculations that were used to calculate static and dynamic balance of the system and how these affect the design of our engine were investigated. Practical techniques were demonstrated to validate the balance of each component after they had been fabricated.Through testing, the first and second order balance effects were analyzed and the harmonic resonances within the system were identified. The interactions between the harmonic resonances and the first and second order forces were also explored.
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Title: Control of multi-link one-legged hopping locomotion
Creator: Allafi, Amer
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Controlling one-legged hopping locomotion is a challenging problem due to the hybrid dynamics of the hopper and the interaction with ground. The hybrid dynamics of the one-legged hopper consists of mainly two sub-dynamics, one when the hopper is in contact with ground, and the other when there is no contact. The ground model can effect the hopper behavior since the hopper interact with ground when the hopper in contact with ground. Here we investigate the locomotion behavior of the one-legged...
Show moreControlling one-legged hopping locomotion is a challenging problem due to the hybrid dynamics of the hopper and the interaction with ground. The hybrid dynamics of the one-legged hopper consists of mainly two sub-dynamics, one when the hopper is in contact with ground, and the other when there is no contact. The ground model can effect the hopper behavior since the hopper interact with ground when the hopper in contact with ground. Here we investigate the locomotion behavior of the one-legged multi-link hopper hopes on three different ground models, namely, rigid, elastic, and viscoelastic ground. The rigid ground apply an impulsive force to the hopper when the hopper came in contact with ground resulting energy losses. A partial feedback linearization is used to control the internal dynamics of the hopper. A Poincar\\'e map is used to construct a discrete-time system and a controller with integral action is designed to achieve the control objectives. The elastic ground, the ground modeled as massless spring, the spring in the ground store some of the energy of the hopper during the contact. A continuous backstepping controller is designed to control the energy level and internal dynamics of the hopper. A Poincar\\'e map is used to construct a discrete-time system and a controller with integral action is designed to achieve the control objectives. The viscoelastic ground, the ground modeled as an under-damped mass-spring-damper system, the damper and the impact with ground mass resulting in energy losses and the ground spring store some of the energy of the hopper during the contact. A continuous backstepping controller is designed to control the energy level and internal dynamics of the hopper. A Poincar\\'e map is used to construct a discrete-time system and a controller with integral action is designed to achieve the control objectives. We considered multiple versions of one-legged hoppers, namely, two-DOF two-mass, two-DOF ankle-knee-hip, and four-link hopper. Simulation results are presented to demonstrate the efficacy of the controllers.
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Title: Simulation study of thermal electric circuit
Creator: Yan, Dafa
Date: 2014
Collection: Electronic Theses & Dissertations
Description: Thermoelectric generator works under different working conditions, especially different temperature and load resistance. In order to improve its efficiency, the circuit was in place between thermoelectric generator and load resistance using a buck converter. Compared with the direct connection case the buck converter improves efficiency, especially with small load resistance. Power output and current ripple are the central focus for evaluating this buck converter. Regarding thermoelectric...
Show moreThermoelectric generator works under different working conditions, especially different temperature and load resistance. In order to improve its efficiency, the circuit was in place between thermoelectric generator and load resistance using a buck converter. Compared with the direct connection case the buck converter improves efficiency, especially with small load resistance. Power output and current ripple are the central focus for evaluating this buck converter. Regarding thermoelectric generator characteristic, PMW (pulse-width-modulation) mode is selected for regulating buck converter switch. The tool box selected for building simulation model of buck converter is Simscape in matlab/Simulink. To verify the model, differential equation mathematic model and state-space simulation model are built. To configure the parameters of the buck converter, all the possible data is collected by running simulation model with different sets of parameters. After configuration, the optimal parameters for the buck converter is obtained. A method of selecting optimal parameter set is introduced for the given requirement for the circuit performance.With a set of optimal circuit parameters such as capacitor and inductor values, a controller of PWM signal is to be designed for optimizing the circuit system efficiency, where the extreme seeking control was used. With the controller, it proves that even with different load resistance, the buck converter can delivered maximum power with optimized the duty cycle of PWM.
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Title: Development of a bismuth telluride thermoelectric generator for a vehicle with 3.5 L Ford Ecoboost internal combustion engine
Creator: Ivanov, V. N. (Vasiliĭ Nikolaevich)
Date: 2013
Collection: Electronic Theses & Dissertations
Description: Thermoelectric generator (TEG) is a good opportunity for improving fuel economy and reducing emissions of a vehicle, taking in mind high fuel cost and need for cleaner vehicles. TEG transforms heat to electricity (the Seebeck effect) and could be applied to waste heat in a vehicle. Electricity generated could be used for operating electric motors, powering sensors, or charging a battery.There are two major issues in TEG development for a vehicle: heat transfer considerations and TE material...
Show moreThermoelectric generator (TEG) is a good opportunity for improving fuel economy and reducing emissions of a vehicle, taking in mind high fuel cost and need for cleaner vehicles. TEG transforms heat to electricity (the Seebeck effect) and could be applied to waste heat in a vehicle. Electricity generated could be used for operating electric motors, powering sensors, or charging a battery.There are two major issues in TEG development for a vehicle: heat transfer considerations and TE material selection.The present work describes the efforts directed towards heat transfer considerations and employs bismuth telluride as thermoelectric (TE) material. Effective heat transfer system was developed for TE modules integration into practical TEG as a part of an exhaust system of a vehicle with 3.5L Ford Ecoboost internal combustion (IC) engine. The goal was to optimize the design of a TEG, including size and weight, and to obtain the maximum performance from this device. Experiments were conducted with the TEG developed that simulate real world conditions.
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Title: Resilient and safe control of cyber-physical systems under uncertainties and adversaries
Creator: Mustafa, Aquib
Date: 2020
Collection: Electronic Theses & Dissertations
Description: The recent growth of cyber-physical systems with a wide range of applications such as smart grids, healthcare, search and rescue and traffic monitoring, to name a few, brings new challenges to control systems due to the presence of significant uncertainties and undesired signals (i.e., disturbances and cyber-physical attacks). Thus, it is of vital importance to design resilient and safe control approaches that can adapt to the situation and mitigate adversaries to ensure an acceptable level...
Show moreThe recent growth of cyber-physical systems with a wide range of applications such as smart grids, healthcare, search and rescue and traffic monitoring, to name a few, brings new challenges to control systems due to the presence of significant uncertainties and undesired signals (i.e., disturbances and cyber-physical attacks). Thus, it is of vital importance to design resilient and safe control approaches that can adapt to the situation and mitigate adversaries to ensure an acceptable level of functionality and autonomy despite uncertainties and cyber-physical attacks.This dissertation begins with the analysis of adversaries and design of resilient distributed control mechanisms for multi-agent cyber-physical systems with guaranteed performance and consensus under mild assumptions. More specifically, the adverse effects of cyber-physical attacks are first analyzed on the synchronization of the multi-agent cyber-physical systems. Then, information-theoretic based detection and mitigation methods are presented by equipping agents with self-belief about the trustworthiness of their own information and trust about their neighbors. Then, the effectiveness of the developed approach is certified by applying it to distributed frequency and voltage synchronization of AC microgrids under data manipulation attacks. In the next step, to relax some connectivity assumptions in the network for the resilient control design, a distributed adaptive attack compensator is developed by estimating the normal expected behavior of agents. The adaptive attack compensator is augmented with the controller and it is shown that the proposed controller achieves resilient synchronization in the presence of the attacks on sensors and actuators. Moreover, this approach recovers compromised agents under actuator attacks and avoids propagation of attacks on sensors without discarding information from the compromised agents. Then, the problem of secure state estimation for distributed sensor networks is considered. More specifically, the adverse effects of cyber-physical attacks on distributed sensor networks are analyzed and attack mitigation mechanism for the event-triggered distributed Kalman filter is presented. It is shown that although event-triggered mechanisms are highly desirable, the attacker can leverage the event-triggered mechanism to cause triggering misbehaviors which significantly harms the network connectivity and performance. Then, an entropy estimation-based attack detection and mitigation mechanisms are designed.Finally, the safe reinforcement learning framework for autonomous control systems under constraints is developed. Reinforcement learning agents with pre-specified reward functions cannot provide guaranteed safety across variety of circumstances that an uncertain system might encounter. To guarantee performance while assuring the satisfaction of safety constraints across variety of circumstances, an assured autonomous control framework is designed by empowering reinforcement learning algorithms with meta-cognitive learning capabilities. More specifically, adapting the reward function parameters of the reinforcement learning agent is performed in a meta-cognitive decision-making layer to assure the feasibility of the reinforcement learning agent.
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Title: Exploiting impulsive inputs for stabilization of underactuated robotic systems : theory and experiments
Creator: Kant, Nilay
Date: 2020
Collection: Electronic Theses & Dissertations
Description: Robots have become increasingly popular due to their ability to perform complex tasks and operate in unknown and hazardous environments. Many robotic systems are underactuated i.e., they have fewer control inputs than their degrees-of-freedom (DOF). Common examples of underactuated robotic systems are legged robots such as bipeds, flying robots such as quadrotors, and swimming robots. Due to limited control authority, underactuated systems are prone to instability. This work includes...
Show moreRobots have become increasingly popular due to their ability to perform complex tasks and operate in unknown and hazardous environments. Many robotic systems are underactuated i.e., they have fewer control inputs than their degrees-of-freedom (DOF). Common examples of underactuated robotic systems are legged robots such as bipeds, flying robots such as quadrotors, and swimming robots. Due to limited control authority, underactuated systems are prone to instability. This work includes impulsive inputs in the set of admissible controls to address several challenging control problems. It has already been shown that continuous-time approximation of impulsive inputs can be realized in physical hardware using high-gain feedback.Stabilization of an equilibrium point is an important control problem for underactuated systems. The ability of the system to remain stable in the presence of disturbances depends on the size of the region of attraction of the stabilized equilibrium. The sum of squares and trajectory reversing methods are combined to generate a large estimate of the region of attraction. This estimate is then effectively enlarged by applying the impulse manifold method to stabilize equilibria from points lying outside the estimated region of attraction. Simulation results are provided for a three-DOF tiptoebot and experimental validation is carried out on a two-DOF pendubot. Impulsive inputs are also utilized to control the underactuated inertia-wheel pendulum (IWP). When subjected to impulsive inputs, the dynamics of the IWP can be described by algebraic equations. Optimal sequences of inputs are designed to achieve rest-to-rest maneuvers and the results are applied to the swing-up control problem. The novel problem of juggling a devil-stick using impulsive inputs is also investigated. Impulsive forces are applied to the stick intermittently and the impulse of the force and its point of application are modeled as inputs to the system. A dead-beat design for one of the inputs simplifies the control problem and results in a discrete linear time invariant system. To achieve symmetric juggling, linear quadratic regulator (LQR) and model predictive control (MPC) based designs are proposed and validated through simulations.A repetitive motion is described by closed orbits and therefore, stabilization of closed orbits is important for many applications such as bipedal walking and steady swimming. We first investigate the problem of energy-based orbital stabilization using continuous inputs and intermittent impulsive braking. The orbit is a manifold where the active generalized coordinates are fixed and the total mechanical energy of the system is equal to some desired value. Simulation and experimental results are provided for the tiptoebot and the rotary pendulum, respectively. The problem of orbital stabilization using virtual holonomic constraints (VHC) is also investigated. VHCs are enforced using a continuous controller which guarantees existence of closed orbits. A Poincare section is constructed on the desired orbit and the orbit is stabilized using impulsive inputs which are applied intermittently when the system trajectory crosses the Poincare section. This approach to orbital stabilization is general, and has lower complexity and computational cost than control designs proposed earlier.
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Title: Experiments and model development of a dual mode, turbulent jet ignition engine
Creator: Tolou, Sedigheh
Date: 2019
Collection: Electronic Theses & Dissertations
Description: "The number of vehicles powered by a source of energy other than traditional petroleum fuels will increase as time passes. However, based on current predictions, vehicles run on liquid fuels will be the major source of transportation for decades to come. Advanced combustion technologies can improve fuel economy of internal combustion (IC) engines and reduce exhaust emissions. The Dual Mode, Turbulent Jet Ignition (DM-TJI) system is an advanced, distributed combustion technology which can...
Show more"The number of vehicles powered by a source of energy other than traditional petroleum fuels will increase as time passes. However, based on current predictions, vehicles run on liquid fuels will be the major source of transportation for decades to come. Advanced combustion technologies can improve fuel economy of internal combustion (IC) engines and reduce exhaust emissions. The Dual Mode, Turbulent Jet Ignition (DM-TJI) system is an advanced, distributed combustion technology which can achieve high diesel-like thermal efficiencies at medium to high loads and potentially exceed diesel efficiencies at low-load operating conditions. The DM-TJI strategy extends the mixture flammability limits by igniting lean and/or highly dilute mixtures, leading to low-temperature combustion (LTC) modes in spark ignition (SI) engines. A novel, reduced order, and physics-based model was developed to predict the behavior of a DM-TJI engine with a pre-chamber air valve assembly. The engine model developed was calibrated based on experimental data from a Prototype II DM-TJI engine. This engine was designed, built, and tested at the MSU Energy and Automotive Research Laboratory (EARL). A predictive, generalized model was introduced to obtain a complete engine fuel map for the DM-TJI engine. The engine fuel map was generated in a four-cylinder boosted configuration under highly dilute conditions, up to 40% external exhaust gas recirculation (EGR). A vehicle simulation was then performed to further explore fuel economy gains using the fuel map generated for the DM-TJI engine. The DM-TJI engine was embodied in an industry-based vehicle to examine the behavior of the engine over the U.S. Environmental Protection Agency (EPA) driving schedules. The results obtained from the drive cycle analysis of the DM-TJI engine in an industry-based vehicle were compared to the results of the same vehicle with its original engine. The vehicle equipped with the DM-TJI system was observed to benefit from 103033% improvement in fuel economy and 103031% reduction in CO2 emission over the EPA combined city/high driving schedules. Potential improvements were discussed, as these results of the drive cycle analysis are the first-ever reported results for a DM-TJI engine embodied in an industry-based vehicle. The resulting fuel economy and CO2 emission were used to conduct a cost-benefit analysis of a DM-TJI engine. The cost-benefit analysis followed the economic and key inputs used by the U.S. EPA in a Proposed Determination prepared by that agency. The outcomes of the cost-benefit analysis for the vehicle equipped with the DM-TJI system were reported in comparison with the same vehicle with its base engine. The extra costs of a DM-TJI engine were observed to be compensated over the first three years of the vehicle's life time. The results projected maximum savings of approximately 2400 in 2019 dollars. This includes the lifetime-discounted present value of the net benefits of the DM-TJI technology, compared to the base engine examined. In this dollar saving estimate, the societal effects of CO2 emission were calculated based on values by the interagency working group (IWG) at 3% discount rate."--Pages ii-iii.
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Title: A hybrid system approach to impedance and admittance control
Creator: Mathis, Frank
Date: 2012
Collection: Electronic Theses & Dissertations
Description: Impedance Control and Admittance Control are two different implementation methods that are used to achieve the same control objective of producing a desired relationship between applied force and displacement of a robotic system interacting with an environment. Due to the difference in implementation method, impedance control and admittance control have complementary performance and stability characteristics. Impedance control is stable for all contact environment stiffness and has good...
Show moreImpedance Control and Admittance Control are two different implementation methods that are used to achieve the same control objective of producing a desired relationship between applied force and displacement of a robotic system interacting with an environment. Due to the difference in implementation method, impedance control and admittance control have complementary performance and stability characteristics. Impedance control is stable for all contact environment stiffness and has good performance for stiff environments, but results in poor performance during interaction with soft environments. Admittance control results in good performance during interaction with soft environments but results in either poor performance and or unstable behavior during interaction with stiff environments. We use a hybrid system framework to propose a family of controllers that attempt to interpolate the stability and performance characteristics of impedance control and admittance control. The advantages of this approach are first demonstrated through analysis and simulations of a single degree-of-freedom rigid linear model. The methodology is thenextended to multi degree-of-freedom linear and non-linear models and single degree-of-freedom system with flexibility. Experimental results with a lightweight robotic arm are presented to demonstrate the usefulness of the approach.
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Title: Grid-connected energy storage systems : benefits, planning and operation
Creator: Tian, Yuting
Date: 2018
Collection: Electronic Theses & Dissertations
Description: "Deployment of energy storage systems (ESSs) is gaining significant momentum due to economic incentives, power system regulation requirements, and integration of renewable energy resources. This dissertation covers three aspects of grid-connected ESSs: benefits, planning, and operation. First, the benefits and use cases of ESSs are reviewed and a comprehensive evaluation method for estimating stacked revenue of ESSs is proposed. The stacked revenue from an ESS cannot be calculated by merely...
Show more"Deployment of energy storage systems (ESSs) is gaining significant momentum due to economic incentives, power system regulation requirements, and integration of renewable energy resources. This dissertation covers three aspects of grid-connected ESSs: benefits, planning, and operation. First, the benefits and use cases of ESSs are reviewed and a comprehensive evaluation method for estimating stacked revenue of ESSs is proposed. The stacked revenue from an ESS cannot be calculated by merely aggregating the benefits from various applications (e.g., energy arbitrage, frequency regulation, and outage mitigation) as the ESS may not be available for all types of applications during the same time interval. A model incorporating component reliability, power system operation constraints, and storage system operation constraints is developed to evaluate the composite revenue generated from the applications. Second, for planning purposes, a model to estimate the capacity value of ESSs is developed and a sensitivity guided approach to ESS siting is proposed. In contrast to conventional generators with the capability to provide energy upon demand, ESSs are energy-limited resources. In addition, it is possible that the availability of an ESS is low when it is needed to provide its capacity to maintain system reliability due to low state of charge. Thus, the work presented here proposes a method to evaluate the actual capacity contribution of ESSs, considering the energy-limited characteristic and the availability uncertainty. Also, it is necessary to determine suitable locations so as to maximize the benefit of ESSs. This dissertation proposes a sensitivity guided approach which aims at finding the optimal location of ESSs to reduce the peak hour generation cost. The last part of this dissertation proposes a model to determine the operation strategy of battery ESSs. This algorithm not only attempts to maximize the financial benefits but also considers the cycling behavior and its impact on the longevity of battery energy storage systems."--Page ii.
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Title: The development and analysis of a hydraulically actuated valve for a dual mode turbulent jet iIgnition (DM-TJI) engine
Creator: Myers, Joshua (Graduate of Michigan State University)
Date: 2017
Collection: Electronic Theses & Dissertations
Description: With the increased concern for the affect that the use of internal combustion engines has on the environment, interest in engine technologies that can reduce the emissions has increased significantly. One such example that is being investigated by Michigan State University is the use of a Dual Mode Turbulent Jet Ignition (DM-TJI) to replace the use of a traditional spark plug. A DM-TJI engine can produce a more complete burn of the fuel while also allowing for use of leaner air–fuel mixes...
Show moreWith the increased concern for the affect that the use of internal combustion engines has on the environment, interest in engine technologies that can reduce the emissions has increased significantly. One such example that is being investigated by Michigan State University is the use of a Dual Mode Turbulent Jet Ignition (DM-TJI) to replace the use of a traditional spark plug. A DM-TJI engine can produce a more complete burn of the fuel while also allowing for use of leaner air–fuel mixes resulting in improved fuel economy. Controlling the intake of air into the pre-chamber of the DM-TJI engine is extremely important for it to run properly since controlling the intake of air allows for purging and management of the strength of the ignition jets. To achieve this, a valve that is capable of operating at the speeds necessary to allow for the proper amount of air to enter the prechamber, has been designed and is under final fabrication. The purpose of this thesis is a proof of concept experiment and analysis. Areas of improvement have been identified and once viable modifications have been recommended.
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Title: Three dimensional analysis of the gas flow in piston ring pack
Creator: Kharazmi, Ali
Date: 2017
Collection: Electronic Theses & Dissertations
Description: "Cylinder-kit dynamics design in an internal combustion engine is highly relevant for the engine performance characteristics, durability and reliability. Since the middle of the 20th century, researchers have been using numerical models to describe the processes that occur in a ring pack. Because it is difficult and extremely costly to conduct experiments on every series of engines to check for the blow-by and oil consumption, a computational analysis can be performed on the ring pack to...
Show more"Cylinder-kit dynamics design in an internal combustion engine is highly relevant for the engine performance characteristics, durability and reliability. Since the middle of the 20th century, researchers have been using numerical models to describe the processes that occur in a ring pack. Because it is difficult and extremely costly to conduct experiments on every series of engines to check for the blow-by and oil consumption, a computational analysis can be performed on the ring pack to study the blow-by and oil-consumption characteristics. In this dissertation a 3D CFD simulation model is introduced to analyze the flow between the cylinder liner and the piston. This model allows for calculation of the piston assembly with consideration of the ring dynamics, transient boundary conditions for combustion chamber pressure and temperature as well as thermal distortion of the piston and liner. The determination of the complex geometry of the cylinder-kit is established in a STL (STereoLithography) format by considering the complicated geometrical details of the ring pack such as thermal distortion of piston and liner, ring twist and ring/groove conformability. The blow by and blow back is numerically calculated for a small bore cylinder operating at 2000 RPM and verified by the results of commercially available 1D models. The calculated velocity filed shows substantial circumferential flow in the piston ring pack that is dominated by the ring and groove geometry as well as the relative position of the rings end gap. It is found that the amount of gas that flows back to the combustion chamber increases when the in-cylinder pressure trace decreases from its peak value. The knowledge from this study can be used as a basis for further multiphase calculations containing oil flow such as oil consumption, oil evaporation and eventually cylinder-kit wear."--Page ii.
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Title: Numerical modeling of the power cylinder system for internal combustion engine with an emphasis on ring pack design
Creator: Cheng, Chao (Mechanical engineer)
Date: 2014
Collection: Electronic Theses & Dissertations
Description: Modeling the piston ring behavior is crucial for the engine power cylinder system. The dynamic and thermal characteristics directly affect engine performance, e.g. frintion loss, wear, blowby loss, etc. This dissertation describes a numerical model of the power cylinder system focusing on the ring pack design. A three-dimensional piston ring model is developed using finite element method. The model predicts the piston ring conformability with the cylinder wall as well as the separation gap...
Show moreModeling the piston ring behavior is crucial for the engine power cylinder system. The dynamic and thermal characteristics directly affect engine performance, e.g. frintion loss, wear, blowby loss, etc. This dissertation describes a numerical model of the power cylinder system focusing on the ring pack design. A three-dimensional piston ring model is developed using finite element method. The model predicts the piston ring conformability with the cylinder wall as well as the separation gap between the interfaces. In addition, the ring model also predicts the interaction between the ring and piston groove sides. This means, the ring axial lift, twist, contact with the groove sides along the circumferential direction are all calculated simultaneously with the radial conformability prediction. The numerical model is then verified through experiment measurement. This validation includes a ring tension force measurement as well as a light-tightness measurement. Good agreement has been found between the measured and calculated result. Thermal load is believed having significant influence on the ring pack performance, especially for the top compression ring, which is under the most severe operating condition. The thermal load influences are included in the model. In addition, a new lubrication model is implemented to the existing model with the consideration of flow factor for the ring pack lubrication and tribology analysis. A simulation study of the second ring dynamics for a modern diesel engine is presented. Two phenomena are focused for this study, one is the second ring fluttering and the other is ring collapse. Both these phenomena are closely related to gas dynamics and could result in engine blowby increase. The mechanism and the conditions at which these phenomena occur are given. The second ring dynamic behavior over an engine cycle is then studied considering 3D effect. The contact forces, in both radial and axial directions, and the twist angles can be found at each engine crank angle. The piston ring model provides the geometry for three-dimensional gas dynamics analysis. In addition to the gas flow paths that the current two-dimensional models predict, including through the ring end gap, through the ring-groove sides as ring flutters, through the ring front face when ring radially collapses, gas can flow through an additional path across the ring. This gas flow path is formed due to the variance of ring axial displacements along the circumference. The variant lift occurs for rings with asymmetric cross-sections. Even for rings with symmetric cross-section, the ring can also undergo different circumferential lift due to influences like piston secondary motion. When this different circumferential lift occurs, gas can flow from the piston land above the ring, through the crevice between the ring-groove sides, to the volume behind the ring for the ring segment that stays bottom seated. The gas can travel circumferentially through the volume behind the ring, until a point that the ring segments lift and stay top seated against the groove top side. Then the gas can flow from the volume behind the ring, through the crevice between the ring-groove bottom sides, to the piston land below the ring.
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Title: Control of systems with hysteresis using servocompensators
Creator: Esbrook, Alexander James
Date: 2012
Collection: Electronic Theses & Dissertations
Description: The tracking problem in systems with hysteresis has become an important topic of research in the past two decades, due in large part to advances in smart material actuators. In particular, applications like Scanning Probe Microscopy require high performance from hysteretic smart material actuators. Servocompensators, or internal model controllers, have been used successfully in many varieties of tracking problems for both linear and nonlinear systems; therefore, their application to systems...
Show moreThe tracking problem in systems with hysteresis has become an important topic of research in the past two decades, due in large part to advances in smart material actuators. In particular, applications like Scanning Probe Microscopy require high performance from hysteretic smart material actuators. Servocompensators, or internal model controllers, have been used successfully in many varieties of tracking problems for both linear and nonlinear systems; therefore, their application to systems with hysteresis is considered in this dissertation. The use of Multi-Harmonic Servocompensators (MHSC) is first proposed to simultaneously compensate for hysteresis and enable high-bandwidth tracking in systems with hysteresis, such as nanopositioners. With the model represented by linear dynamics preceded with a Prandtl-Ishlinskii hysteresis operator, the stability and periodicity of the closed-loop system's solutions are established when hysteresis inversion is included in the controller. Experiments on a commercial nanopositioner show that, with the proposed method, tracking can be achieved for a 200 Hz reference signal with 0.52% mean error and 1.5% peak error over a travel range of 40 μm. Additionally, the proposed method is shown at high frequencies to be superior to Iterative Learning Control (ILC), a common technique in nanopositioning control.The theoretical and practical weaknesses of the proposed approach are then addressed. First, the design of a novel adaptive servocompensator specialized to systems with hysteresis is presented, based on frequency estimation coupled with slow adaptation, and the stability in cases with one, two, or n unknown frequencies are established. Next, a condition in the form of a Linear Matrix Inequality is presented proving the stability of the proposed MHSC when hysteresis inversion is not used. It is then experimentally demonstrated that removing hysteresis inversion further reduces the tracking error achievable by the MHSC. Finally, the properties of self-excited limit cycles are studied for an integral-controlled system containing a play operator. A Newton-Raphson algorithm is formulated to calculate the limit cycles, and linear relationships between the amplitude and period of these limit cycles and system parameters are obtained.
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Title: Microbial fuel cells : design, control-oriented modeling, and experimental results
Creator: Abul, Ali
Date: 2015
Collection: Electronic Theses & Dissertations
Description: There is no doubt about how crucial to have sustainable energy in this era. Researchers focus on fuel cells because of their high efficiency, environmental friendliness, and independence from limited sources, etc. Microbial fuel cell (MFC) is a promising technology that responds to the demand of sustainable energy. MFCs, similar to other fuel cells, use catalysts and produce electricity through chemical reactions during substrate break-down. In this case, MFCs use bacteria as the catalysts to...
Show moreThere is no doubt about how crucial to have sustainable energy in this era. Researchers focus on fuel cells because of their high efficiency, environmental friendliness, and independence from limited sources, etc. Microbial fuel cell (MFC) is a promising technology that responds to the demand of sustainable energy. MFCs, similar to other fuel cells, use catalysts and produce electricity through chemical reactions during substrate break-down. In this case, MFCs use bacteria as the catalysts to break down the organic matter. There have been control studies on fuel cells, specifically on hydrogen fuel cells, for various purposes. Because MFCs are still not well understood, similar control studies have not been adequately conducted. In this study, a control-oriented mathematical model for MFC dynamics is developed and analyzed. An MFC system is designed and developed, which has successfully demonstrated production of electricity. Experiments are conducted to identify the model parameters and validate the model. For the MFC prototype, \textit{G. sulfurreducens} strain PCA is used as the pure bacteria culture with the acetate as the substrate. The MFC used in this study adopts a membrane-less single-chamber configuration, and utilizes an air-cathode and a carbon-brush anode.Once the model is developed, the behavior of an MFC is analyzed using system theory. In particular, the equilibria of the system in the continuous mode, where the MFC is fed with the substrate at a constant rate are computed. Furthermore, Jacobian analysis and phase portraits are used to understand the stability properties of the equilibria.
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