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Abiakel, ElioDevelopment of an undergraduate laboratory course in control systems
Master of Science, The Ohio State University, 2003, Electrical Engineering
This thesis serves as a guideline for the development of a full one-term undergraduate laboratory course in control systems. The work presented here is mainly of experimental nature with emphasis on measurement, data acquisition and control design and analysis. The challenge behind this project was the adaptation of classical teaching and experiments in control systems to the state-of-the art implementation technologies used in the industry worldwide, while maintaining and improving the pedagogical aspects of the methodology previously followed in the Department of Electrical Engineering at The Ohio State University. First we introduce the hardware and software used in the laboratory, i.e. Quanser Consulting equipment, dSPACE computer cards and software packages, and Matlab and Simulink (Chapter 1). Then we present two laboratory experiments (Chapters 2 & 3) that serve as a tutorial introduction to these hardware and software and to digital signal processing. The next two experiments (Chapters 4 & 5) deal with system identification and basic control design using gain compensation. We then develop a series of experiments on DC servomotors to treat classical design methods such as root locus, lead, lag and PID control design (Chapters 6 through 8). We follow that with a set of experiments on more advanced apparatus such as flexible links and flexible joints (Chapters 9 &10). Chapters 11, 12, and 13 are dedicated to linear quadratic regulator (LQR) control design for the flexible joint, the flexible link and the two-degree-of-freedom helicopter; even though these chapters are not intended for use in an undergraduate laboratory course, their content can be used to develop demonstration experiments that can be presented at the beginning or the end of the term. Finally we conclude with general comments and recommendations for the future, along with an Appendix that contains an instructor’s guide.

Committee:

Stephen Yurkovich (Advisor)

Keywords:

Control Systems Lab; Control Laboratory; EE557; dSPACE; Quanser; Simulink; Matlab; root locus; feedback control; signals and systems; Helicopter control; flexible link; flexible joint; DC servo, servomotor; speed control; position control

Garimella, SureshActuator Modeling and Control For a Three Degrees of Freedom Differential Thrust Control Testbed
Master of Science (MS), Ohio University, 2007, Electrical Engineering & Computer Science (Engineering and Technology)
This thesis presents an improvement in the performance of a three degrees of freedom differential thrust control testbed by considering the actuator dynamics. The testbed consists of three propellers that are used to produce thrust as well as attitude control for vertical takeoff and landing flight. Actuator dynamics consist of the motor-propeller dynamics and the nonlinear mapping relating the aerodynamic torques to the propeller speed. A previous controller was designed by neglecting the motor-propeller dynamics and the control allocation was done assuming a linear static relationship between aerodynamic torques and motor voltages. This work will determine the nonlinear control allocation mapping and model the motor-propeller dynamics as a first-order linear system. Simulation and real-time results showing an improvement in the performance of the testbed are presented by replacing the linear control allocation with nonlinear control allocation and by compensating for the motor-propeller dynamics. Further, the existing controller is redesigned considering the gyroscopic effects produced due to the spinning propellers.

Committee:

Jianchao Zhu (Advisor)

Keywords:

Nonlinear Control Allocation; Actuator Dynamics; DC Motor-propeller dynamics; Differential thrust control testbed; Trajectory Linearization Control; MATLAB/Simulink; Open-loop control; Closed-loop control

Kim, ByeongilDesign and Analysis of Model Based Nonlinear and Multi-Spectral Controllers with Focus on Motion Control of Continuous Smart Structures
Doctor of Philosophy, The Ohio State University, 2010, Mechanical Engineering

Smart structures are currently utilized in many applications from precision positioning control of large space structures to active vibration control of machine components. Despite their relative easiness in controlling, positioning accuracy and longevity can be compromised by the hysteresis. In addition, current active control algorithms are limited predominantly to the control of a single or multiple sinusoidal waves and these are incapable of addressing more complicated multi-spectral signals such as modulated signatures. This dissertation introduces model-based and nonlinear control techniques aimed at the reduction of hysteretic effect and for their application to active motion control.

A nonlinear energy-based hysteresis model is developed for a piezoelectric stack actuator and model predictive sliding mode control is applied to force the system state to reach a sliding surface in an optimal manner and to accurately track the reference signal. This method is employed on pre-stressed curved unimorph actuators (modeled by a second order differential equation) with an additional time delay term to describe the hysteretic effect. Simulations and experiments are conducted to validate this approach, and the results highlight significantly improved hysteresis reduction in the displacement control mode. Also, it has been verified that the performance of the novel control methods is not much affected by the accuracy of actuator model.

Next, enhanced adaptive filtering algorithms are developed with application to active vibration control. A feedback loop with the model predictive sliding mode control is introduced in the adaptive filtering system. The goal of this study is to manage multi-spectral signals while achieving smooth and effective convergence, self-adaptability, and stability. The performance for new adaptive filtering algorithms is validated numerically and experimentally for different signals and other prevailing characteristics. The proposed algorithms are also compared with traditional algorithms for both narrowband and broadband control of signals with complex frequency spectra. The novel technique deals with primary peaks, sidebands, and broadband level simultaneously without a full knowledge of the unwanted signals.

Committee:

Gregory Washington, PhD (Advisor); Rajendra Singh, PhD (Advisor); Vadim Utkin, PhD (Committee Member); Marcelo Dapino, PhD (Committee Member)

Subjects:

Engineering

Keywords:

model based control; smart structures; nonlinear control; multi-spectral control; motion control; hysteresis; active vibration control

Kotecha, Ramchandra M.Analysis and Comparison of Popular Models for Current-Mode Control of Switch Mode Power Supplies
Master of Science in Engineering (MSEgr), Wright State University, 2011, Electrical Engineering
Current-mode control is the most popular scheme used for the operation of SMPS (Switch Mode Power Supplies). Current-mode control, also known as current-programmed mode or current-injected control is a multi-loop control scheme that has an inner loop and an outer voltage loop. The current loop controls the inductor peak current while the voltage loop controls the output voltage. The inner loop follows a set program by the outer loop. Some of the most popular small-signal models that predict the small-signal characteristics of current-mode control scheme have been analyzed and compared in this thesis. A PWM dc-dc buck converter in CCM(Continuous Conduction Mode) has been chosen to explain the phenomenon of current-mode control in all these models. Small-signal characteristics are generated in MATLAB using the simplified analytical transfer functions. Some of the important small-signal characteristics include the current loop gain, control-to-output gain with the current-loop closed and outer loop open, audio susceptibility, and output impedance. The two most important models in consideration are: 1) Continuous-Time Model and 2) Peak Current-Mode control Model. Despite the fact that both these models predict the instability of current-mode control at a duty ratio of 0.5, these models differ significantly in deriving the expression for the sampling gain. As a result, their small-signal characteristics differ over a wide frequency range. Also, a very less explored average current mode control is compared with the peak-current mode control based on the similar small-signal characteristics.

Committee:

Marian Kazimierczuk, PhD (Advisor); Marian Kazimierczuk, PhD (Committee Chair); Saiyu Ren, PhD (Committee Member); Zhang Xiaodang, PhD (Committee Member)

Subjects:

Electrical Engineering

Keywords:

Current-mode control; SMPS; Switch Mode Power Supplies; Power Electronics; Peak current-mode control; small-signal modelling for current-mode control; voltage mode control; control schemes for pwm dc-dc converters; pwm dc-dc converters

Sigthorsson, David O.Control-Oriented Modeling and Output Feedback Control of Hypersonic Air-Breathing Vehicles
Doctor of Philosophy, The Ohio State University, 2008, Electrical and Computer Engineering
Hypersonic air-breathing vehicles are a promising and cost-efficient technology for launching low-earth-orbit satellites and providing rapid global-response capabilities. Modeling and control of such vehicles has been an active subject of research in recent years. A first-principle, physics-based model (FPM) of the vehicle's longitudinal dynamics has been developed at the Air Force Research Laboratory, and made available to the academic community for control systems design. This model, while suitable for simulation, is intractable for model-based control, thus requiring further control-oriented modeling. A typical control objective is to track a velocity and altitude reference while maintaining physical feasibility of the control input and the state. Two control strategies are presented in this work. The first is a linear time invariant (LTI) design based on a novel formulation of a robust servo-mechanism using singular perturbation arguments. This approach does not rely on state reconstruction but does require an analysis of a family of linearized models from the FPM. The second design relies on reduced-complexity modeling of the FPM. Intractable expressions of the forces and moment in the FPM are replaced with a curve-fit model (CFM). The CFM is expressed as a linear parameter varying (LPV) system, where the scheduling variables depend on the system output. A novel LPV regulator design methodology is developed, which explicitly addresses the case of over-actuated models (i.e., models with more inputs than performance outputs). This is a non-trivial extension of the analysis and design of output regulators for LTI systems. The LPV regulator separates the control problem into a steady-state controller and a stabilizing controller. The steady-state controller produces a non-unique approximate steady-state using receding horizon constrained optimization, while the stabilizer renders the steady-state attractive. The steady-state controller represents an approach to addressing over-actuated LPV systems, alternative to static or dynamic control allocation, or standard optimal control. The stabilizer design utilizes the LPV separation principle to decompose the problem into state feedback and LPV reduced order observer design. Both approaches are applied to the FPM in simulation and their merits and drawbacks discussed.

Committee:

Andrea Serrani, PhD (Advisor); Stephen Yurkovich, PhD (Committee Member); Kevin Passino, PhD (Committee Member)

Subjects:

Electrical Engineering; Engineering

Keywords:

Electrical Engineering; Control Design; LPV Modeling; LPV Control; MIMO systems; Hypersonic Air-Breathing Vehicles; Non-Linear Modeling; Control Oriented Modeling; System ID; Over-Actuated Systems; LPV Regulator; Robust Control; Output-Feedback Control

Choi, JinbaeClosed-Loop Optimal Control of Discrete-Time Multiple Model Linear Systems with Unknown Parameters
Doctor of Philosophy, Case Western Reserve University, 2016, EECS - System and Control Engineering
The closed-loop optimal control of multiple model linear systems with unknown parameters is investigated. The Bellman equation is modified to include the discrete random variable of the system mode conditioned on the measurements, and is then used to determine the optimal state feedback or dynamic output feedback controllers. Dynamic programming with the modified Bellman equation is used to calculate the optimal cost with the dual covariance. The dual covariance quantifies the probing aspects of the controller and is demonstrated that the closed-loop state or dynamic output feedback controllers have the dual property for the discrete-time multiple model linear systems with unknown parameters studied in this work. Monte Carlo simulations are used to show that the closed-loop control with state or dynamic output feedback always performs better than controllers such as the Certainty Equivalence or DUL controllers. Finally, the direct discrete-time implementation of the dual dynamic output feedback controller developed in this work is applied to the control of the nonlinear F-16 aircraft. The dual regulator is designed for stability augmentation in the context of reconfigurable control using the multiple model formulation integrated with flight and propulsion to accommodate sensor, actuator, and engine faults. The design process is explained in the context of trim, linearization, calculation of the mode probabilities, and tuning of the Kalman filters and includes the implementation of a six-stage dual regulator with a bank of parallel Kalman filters. The flight simulation results are presented for cases such as speed and pitch rate sensor faults, 1.5% and 3% losses of elevator actuator power, and 4% loss of engine power during steady-state level flight of the nonlinear F-16 aircraft model.

Committee:

Kenneth Loparo, PhD (Advisor); Marc Buchner, PhD (Committee Member); Vira Chankong, PhD (Committee Member); Richard Kolacinski, PhD (Committee Member)

Subjects:

Aerospace Engineering; Electrical Engineering

Keywords:

Closed-loop optimal control; multiple model linear systems; dynamic programming; adaptive dual control; optimal dual dynamic output-feedback regulator; reconfigurable control; integrated flight and propulsion; nonlinear aircraft control

Kratz, Jonathan L.Robust Control of Uncertain Input-Delayed Sample Data Systems through Optimization of a Robustness Bound
Master of Science, The Ohio State University, 2015, Aero/Astro Engineering
A large number of physical continuous-time systems are controlled using digital controllers. These systems are often referred to as sample data systems or hybrid systems and they have become the norm for many real world applications. With this in mind, the impact of modeling uncertainties and time delay are considered. Maintaining stability in a system is of the upmost importance for any control system but the models which are used to develop the control laws which control the actual system are not perfect, being subject to a variety of uncertainties and errors. The goal of a robust control law is to guarantee the stability despite the uncertainty that may exist in the system while a nominal control law is designed with only single perfectly modeled design point in mind. Despite the drive toward hybrid systems in application, the focus in developing robust control methods for uncertain systems, especially as it applies to input-delayed sample data systems, has been more geared toward strictly continuous-times systems or strictly discrete-time systems. Here a methodology for designing robust digital controllers to stabilize uncertain continuous-time systems when subject to a given range of elemental uncertainty an input-delay is set forth. The inspiration for this research grew out of the challenges of implementing a distributed engine control system for gas turbine engines on aerospace vehicles. As a precursor to the development of the robust control methodology presented in this document, a study was conducted to better understand the impact of uncertainty and time delay on gas turbine engines with a vision toward implementing distributed engine control. Simulation results using linearized models of the GE T700 Turboshaft Engine and the NASA developed generic twin-spool engine model C-MAPSS40k suggest that the gas turbine engine is inherently robust in its ability to maintain stability but still no guarantee of its stability can be made using strictly nominal control design techniques. Also noted is that there is an infinite number of uncertainty and time-delay scenarios which may occur, all of which stability should be essentially guaranteed. Therefore the holdup in implementing distributed engine control and reaping its benefits may not be a matter of maintaining stability in reality but guaranteeing that stability will be maintained when subject to the new challenges that come with distributed engine control. Mainly this means addressing the potential for substantial time delay through data transmission and data loss. A published robust control design technique in the continuous-time domain for treating uncertainties was implemented and was shown to provide adequate performance demonstrating that robust controllers can provide good performance with the added piece of mind that the system will remain stable against uncertainties in the system. The study suggested that a digital control law that guarantees stability against both model uncertainties and time delay would be useful and so the momentum from this study was used to develop the robust control method presented here. The method involves converting the uncertain continuous-time system into the discrete-time domain and using an optimization scheme to achieve a control gain which satisfies the stability conditions that followed from the derivation of a discrete-time robustness bound. The power of the technique rests largely on the visualization of the delay in the system as a source of uncertainty rather than a separate part of the problem. A framework for the design methodology has been set forth which has also been extended to treat measurement feedback control and observer-based control in addition to full-state feedback control. In each case examples have been provided. The method is flexible and widely applicable.

Committee:

Rama Yedavalli, Dr. (Advisor); Herman Shen, Dr. (Committee Member)

Subjects:

Aerospace Engineering

Keywords:

robust control, digital control, sample data systems, discrete time systems, input delay, bound, simulation, linear, state space, full-state feedback, measurement feedback, observer-based control, gas turbine engines, distributed engine control

Devarakonda, NaginiEco-inspired Robust Control Design for Linear Dynamical Systems with Applications
Doctor of Philosophy, The Ohio State University, 2011, Aero/Astro Engineering
Recently, the idea of using Ecological Sign Stability approach for designing robust controllers for engineering systems has attracted attention with promising results. In this work, continued research on this topic is presented. It is well known that, in the field of control systems, key to a good controller design is the choice of the appropriate nominal system. Since it is assumed that the perturbations are about this nominal, the extent of allowed perturbation to maintain the stability and/or performance very much depends on this ‘nominal’ system. Therefore, it is evident that this nominal system must have superior robustness properties. Incorporating certain robustness measures proposed in the literature, control design techniques have been realized in state space framework. However, the variety of controllers in state space framework is not as large as that of robust control design methods in frequency domain. Even these very few methods tend to be complex and demand some specific structure to the real parameter uncertainty (such as matching conditions). Overall, the success of all these methods for application to complex aerospace systems is still a subject of debate. Hence, there is still significant interest in designing robust controllers which can perform better than the existing controllers. Addressing these issues, current research proposes that the stability robustness measures for parameter perturbation are considerably improved if the ‘nominal’ system is taken (or driven) to be a ‘sign stable’ system. Motivated by this observation, a new method for designing a robust controller for linear uncertain state space systems is proposed. The novelty of this research lies in the incorporation of ecological principles in order to design robust controllers for engineering systems. It is observed that an ecological perspective gives better understanding of the dynamics of the open and closed loop system (nominal) matrices. One of the attractive features of this controller is that the robustness measure, enters the control design in an explicit manner. The result of implementing controllers inspired by ecological principles simplifies the control algorithm and for certain dynamic systems, greatly reduces computational effort required in the synthesis of the controller. Accurate synthesis of the control algorithms results in ‘most robust’ nominal system (closed loop system). Variations of this control design method that address different categories of uncertainty are presented. The resulting control design methods are illustrated with application to aircraft and spacecraft flight control and aircraft turbine engine control.

Committee:

Rama K. Yedavalli, PhD (Advisor); Meyer Benzakein, PhD (Committee Member); Hooshang Hemami, PhD (Committee Member)

Subjects:

Aerospace Engineering

Keywords:

Robust Control; Linear Uncertain Systems; Ecology; Sign Stability; Aircraft Control; Spacecraft Control; Aircraft Engine Control

Cai, HaiweiModeling and Control of Dual Mechanical Port Electric Machine
Doctor of Philosophy, The Ohio State University, 2015, Electrical and Computer Engineering
The Dual Mechanical Port (DMP) electric machine has two rotors that can be set to rotate at different speeds and directions. Compared to conventional electric machines with only one rotor, the DMP machine provides higher torque density and much better control flexibility. However, the DMP machine has a relatively complex structure, which makes it a challenge to model and control. In addition, the existing model and control algorithms for single rotor machines cannot directly be applied to the DMP machine. In this study, it has been explore that how the DMP machine can be applied to hybrid electric vehicles as an avenue for explaining the electromagnetic characteristics and functionality of this more complex mechanism. The model and the control algorithms for two different DMP machines are also investigated. The first DMP machine, which is called the PMDMP, uses two layers of permanent magnets within the outer rotor. The second one, which is referred to as the SCDMP machine, uses a single layer of squirrel cage within the outer rotor, The study of the modeling and control for the SCDMP machine is the major contribution of this work. Compared to other DMP machines, the PMDMP machine stands out for its high torque density and high efficiency. A detailed model derivation for the PMDMP is presented later in the work. The independent control of its two rotors is investigated and verified by simulations and experiments. To overcome the problems brought about by the position sensors, the effectiveness of position sensorless control algorithms for the PMDMP is investigated. High frequency injection and sliding mode sensorless control algorithms are applied to the PMDMP machine at low speed and high speed, respectively. The performance of the sensorless control algorithms in experiments matches well with the simulation results. To verify the functionality of the DMP machine in power split hybrid application, the power flow pattern in various operational modes are discussed and simulated. To avoid using high cost rare earth permanent magnets, the SCDMP machine is proposed. In this DMP machine, the permanent magnets in the outer rotor is replaced with a squirrel-cage. Therefore, it is referred to as the SCDMP machine. First, the electromagnetic characteristic of the SCDMP machine is analyzed. Then, the transient model and steady-state model of the SCDMP machine are derived. The proposed machine models were then verified by implementing finite element method and simulation. The results showed that the proposed models accurately represent the unique electromagnetic characteristics of the SCDMP machine. Due to these unique characteristics, control algorithms for conventional machines cannot be applied to the SCDMP machine. The methods to calculate the correct current commands and to estimate the outer rotor flux position are proposed. Based on these two methods, a control algorithm for the SCDMP machine is proposed and estimated by simulation. The results showed that the proposed control algorithm is able to independently control the torque productions and the flux levels of the SCDMP machine's two rotors.

Committee:

Longya Xu, Dr. (Advisor); Jin Wang, Dr. (Committee Member); Mahesh Illindala, Dr. (Committee Member)

Subjects:

Electrical Engineering; Electromagnetics; Energy

Keywords:

Finite Element Analysis, Motor Control,Squirrel Cage Motor, Dual Mechanical Port, Electric Machine Modeling, Hybrid Electric Vehicle, Field Oriented Control, Sensorless Control, Independent Control

Saluru, Deepak ChaitanyaActive Fault Tolerant Model Predictive Control of a Turbofan Engine using C-MAPSS40k
Master of Science, The Ohio State University, 2012, Aero/Astro Engineering

Aircraft engine control is a crucial component for the safe and stable operation of gas turbine engines which are complex nonlinear systems. As engines have evolved to higher capabilities it is crucial to update the control strategy to ensure maximum functionality of the engine. Current industrial baseline controllers are based in the Proportional-Integral-Derivative (PID) control scheme along with individual limit controllers having critically damped responses housed in the min-max architecture.

In light of the distributed engine control architecture that exploits digital electronics and hence higher on-board computational capabilities, the baseline controller is replaced by a Model Predictive Control (MPC) law with on-line optimization. MPC is a model based control technique that can handle complex constrained dynamics thus allowing the incorporation of component faults in the design process of the controller. Component faults occur during an engine's operation mainly due to fan blade-shroud rubbing, structural wear and tear and foreign object ingestion thus affecting the engine performance.

Simulations on the Linear Time Invariant (LTI) as well as the nonlinear turbofan engine of the Commercial Modular Aero-Propulsion System Simulation (C-MAPSS40k) tool are carried out. In the presence of a component fault, active fault tolerant control using the multi-model MPC approach is applied by switching between the MPC blocks, each using its respective LTI reference model.The control of both the fan speed as well as the thrust for a demand profile in the Power Level Angle (PLA) is investigated and the MPC performance is compared with that of the PID controller demonstrating the successful replacement of the baseline controller with an on-line fault tolerant MPC. The thrust control approach using MPC consumes lesser fuel when compared with the fan speed control approach.

Committee:

Rama Krishna Yedavalli, PhD (Advisor); Igor Adamovich, PhD (Committee Member)

Subjects:

Aerospace Engineering

Keywords:

C-MAPSS40k; engine control; fault tolerant control; model predictive control; optimal control;

Kamalasadan, SukumarA New Generation of Adaptive Control: An Intelligent Supervisory Loop Approach
Doctor of Philosophy in Engineering, University of Toledo, 2004, Electrical Engineering
A new class of intelligent adaptive control for systems with complex and multimodal dynamics including scheduled and unscheduled ‘Jumps’, is developed. Those systems are often under the challenge of unforeseen changes due to wide range of operations and/or external influences. The underlying structural feature is an introduction of an Intelligent Supervisory Loop (ISL) to augment the Model Reference Adaptive Control (MRAC) framework. Four novel design formulations are developed which evolve from different methods of conceiving ISL, structured into intelligent control algorithms, and then investigated with comprehensive simulation models of a single link flexible robotic manipulator as well as a six degree of freedom F16 fighter aircraft. The first scheme is a Fuzzy Multiple Reference Model Adaptive Controller (FMRMAC). It consists of a fuzzy logic switching strategy introduced to the MRAC framework. The second is a novel Neural Network Parallel Adaptive Controller (NNPAC) for systems with unmodeled dynamics and mode swings. It consists of an online growing dynamic radial basis neural network, which controls the plant in parallel with a direct MRAC. The third scheme is a novel Neural Network Parallel Fuzzy Adaptive Controller (NNPFAC) for dynamic ‘Jump’ systems showing scheduled mode switching and unmodeled dynamics. The scheme consists of a growing online dynamic Neural Network (NN) controller in parallel with a direct MRAC, and a fuzzy multiple reference model generator. The fourth scheme is a Composite Parallel Multiple Reference Model Adaptive Controller (CPMRMAC) for systems showing unscheduled mode switching and unmodeled dynamics. The scheme consists of an online growing dynamic NN controller in parallel with a direct MRAC, and an NN multiple reference model generator. Extensive feasibility simulation studies and investigations have been conducted on the four proposed schemes, and with results consistently showing that the four design formulations developed in this research, for implementing intelligent supervisory loops into the MRAC framework, are feasible, effective and have immense potential for complex systems control. Even though those two systems are specific in nature, they are true representatives of an important and challenging class of dynamic systems that require the new generation of adaptive controllers developed in this project work.

Committee:

Adel Ghandakly (Advisor)

Keywords:

Intelligent Adaptive Control; Intelligent Supervisory Loop Approach; Fuzzy Multiple Reference Model Adaptive Control; Neural Network Parallel Adaptive Control; Neural Network Parallel Fuzzy Adaptive Control

Wilmot, Timothy AllenIntelligent Controls for a Semi-Active Hydraulic Prosthetic Knee
Master of Science in Electrical Engineering, Cleveland State University, 2011, Fenn College of Engineering
We discuss open loop control development and simulation results for a semi-active above-knee prosthesis. The control signal consists of two hydraulic valve settings. These valves control a rotary actuator that provides torque to the prosthetic knee. We develop open loop control using biogeography-based optimization (BBO), which is a recently developed evolutionary algorithm, and gradient descent. We use gradient descent to show that the control generated by BBO is locally optimal. This research contributes to the field of evolutionary algorithms by demonstrating that BBO is successful at finding optimal solutions to complex, real-world, nonlinear, time varying control problems. The research contributes to the field of prosthetics by showing that it is possible to find effective open loop control signals for a newly proposed semi-active hydraulic knee prosthesis. The control algorithm provides knee angle tracking with an RMS error of 7.9 degrees, and thigh angle tracking with an RMS error of 4.7 degrees. Robustness tests show that the BBO control solution is affected very little by disturbances added during the simulation. However, the open loop control is very sensitive to the initial conditions. So a closed loop control is needed to mitigate the effects of varying initial conditions. We implement a proportional, integral, derivative (PID) controller for the prosthesis and show that it is not a sufficient form of closed loop control. Instead, we implement artificial neural networks (ANNs) as the mechanism for closed loop control. We show that ANNs can greatly improve performance when noise and disturbance cause high tracking errors, thus reducing the risk of stumbles and falls. We also show that ANNs are able to improve average performance by as much as 8% over open loop control. We also discuss embedded system implementation with a microcontroller and associated hardware and software.

Committee:

Dan Simon, PhD (Advisor); Fuquin Xiong, PhD (Committee Member); Lili Dong, PhD (Committee Member)

Subjects:

Electrical Engineering; Engineering

Keywords:

prosthetic control; ANN; artificial neural network; BBO; biogeography based optimization; intelligent control; nonlinear control problem; time varying control problem; evolutionary algorithm; gradient descent

Grupenhof, Kyle D.Continuously Variable Amplification Device for Semi-Active Vibration Control of Seismically Loaded Structures
Master of Science (MS), Ohio University, 2012, Civil Engineering (Engineering and Technology)
Many variable stiffness and damping devices have been proposed in an attempt to mitigate the effects of unwanted vibrations in civil engineering structures. This work proposes a novel variable stiffness or damping device called the Continuously Variable Amplification Device (CVAD) that improves upon past limitations. It consists of a sphere and rollers in series with a spring or damper, and is able to produce a large, continuous, and rapidly varying range of stiffness or damping values. A series of relationships and equations are derived and validated to describe the amplification of the device. A numerical simulation is developed that pairs the CVAD with SSASD and RSASD devices and places it in a seismically excited eight story structure in a supplemental damping role. In addition, centralized control laws are created and applied to the CVAD devices. The results demonstrate the device and its centralized control laws are a marked improvement over the state-of-the-art.

Committee:

Kenneth Walsh, Ph.D (Advisor); Eric Steinberg, Ph.D (Committee Member); Deboriah McAvoy, Ph.D (Committee Member); Douglas Green, Ph.D (Committee Member)

Subjects:

Civil Engineering

Keywords:

structural vibration control; vibration control; semiactive; semi-active; variable stiffness; variable damping; CVAD; VAD; RSASD; SSASD; AVS; Group control; centralized control; S-CVT; spherical continuously variable transmission;

Chadha, AnkitAverage Current-Mode Control
Master of Science in Electrical Engineering (MSEE), Wright State University, 2015, Electrical Engineering
In this thesis, an average current-mode controller is analyzed for controlling power electronic converters. This controller consists of two loops. An inner loop, which senses and controls the inductor current and an outer loop, which is used to control the output voltage and provide reference voltage for the inner current loop. An average current-mode controller averages out high frequency harmonics it senses from the inductor current to provide a smooth DC component. This can be used as a control voltage for a pulse width modulator and produce switching pulses for the power electronic converters. An average current-mode controller can also be designed for a good bandwidth, which helps in accurate tracking of the sensed inductor current. For a better understanding of the operation of an average current-mode controller analytical equations are derived. Many transfer functions, which help analyze the properties of an open loop system, the controller transfer functions and a block diagram representing the converter along with current and voltage-control loops are presented. The block diagram and the transfer functions were used to derive the required controller parameters on MATLAB. The designed converter along with the controller is implemented on SABER circuit simulator. Waveforms representing the analytical equations along with the dynamic properties of the converter with the controller were plotted. The plotted SABER simulations were in agreement with the analytical equations. The designed controller was able to produce a controlled output voltage for step change in input voltage and load resistance, when simulated on SABER. Ripples could be observed in the control voltage of the controller, when designed for a good bandwidth. This was also represented by the derived analytical equations.

Committee:

Marian K. Kazimierczuk, Ph.D. (Advisor); Yan Zhuang, Ph.D. (Committee Member); Lavern Alan Starman, Ph.D. (Committee Member)

Subjects:

Electrical Engineering

Keywords:

Average Current-Mode Control; Buck DC-DC Converter Control; Power electronic converter control; Controls; current-mode control; controller design; magnitude and phase plots; step responses;

Belapurkar, Rohit K.Stability and Performance of Propulsion Control Systems with Distributed Control Architectures and Failures
Doctor of Philosophy, The Ohio State University, 2013, Aero/Astro Engineering
Future aircraft engine control systems will be based on a distributed architecture, in which, the sensors and actuators will be connected to the Full Authority Digital Engine Control (FADEC) through an engine area network. Distributed engine control architecture will allow the implementation of advanced, active control techniques along with achieving weight reduction, improvement in performance and lower life cycle cost. The performance of a distributed engine control system is predominantly dependent on the performance of the communication network. Due to the serial data transmission policy, network-induced time delays and sampling jitter are introduced between the sensor/actuator nodes and the distributed FADEC. Communication network faults and transient node failures may result in data dropouts, which may not only degrade the control system performance but may even destabilize the engine control system. Three different architectures for a turbine engine control system based on a distributed framework are presented. A partially distributed control system for a turbo-shaft engine is designed based on ARINC 825 communication protocol. Stability conditions and control design methodology are developed for the proposed partially distributed turbo-shaft engine control system to guarantee the desired performance under the presence of network-induced time delay and random data loss due to transient sensor/actuator failures. A fault tolerant control design methodology is proposed to benefit from the availability of an additional system bandwidth and from the broadcast feature of the data network. It is shown that a reconfigurable fault tolerant control design can help to reduce the performance degradation in presence of node failures. A T-700 turbo-shaft engine model is used to validate the proposed control methodology based on both single input and multiple-input multiple-output control design techniques.

Committee:

Rama Yedavalli, PhD (Advisor); Meyer Benzakein, PhD (Committee Member); Krishnaswamy Srinivasan, PhD (Committee Member)

Subjects:

Aerospace Engineering

Keywords:

Distributed turbine engine control systems; networked control systems; time delay systems;fault tolerant control systems;robust control systems

Kim, HongjinWAVELET-BASED ADAPTIVE CONTROL OF STRUCTURES UNDER SEISMIC AND WIND LOADS
Doctor of Philosophy, The Ohio State University, 2002, Civil Engineering
A new control algorithm, wavelet-hybrid feedback LMS algorithm, is developed to overcome the shortcomings of the classical feedback control algorithms and the filtered-x LMS control algorithm. It integrates a feedback control algorithm such as the LQR or LQG algorithm with the filtered-x LMS algorithm and utilizes a wavelet multi-resolution analysis for the low-pass filtering of external dynamic excitations. Since the control forces determined by the filtered-x LMS algorithm are adapted by updating the FIR filter coefficients at each sampling time until the output error is minimized, the new control algorithm is effective in control of both steady-state and transient vibrations. It is shown that the algorithm is capable of suppressing vibrations over a range of input excitation frequencies unlike the classic feedback control algorithms whose control effectiveness decreases considerably when the frequency of the external disturbance differs from the fundamental frequency of the system. Further, results demonstrate that the wavelet transform can be effectively used as a low-pass filter for control of civil structures without any significant additional computational burden. A new hybrid control system, hybrid damper-TLCD system, is developed through judicious integration of a passive supplementary viscous fluid damping system with a semi-active TLCD system, and its performance is evaluated for control of responses of 3D irregular buildings under various seismic excitations and for control of wind-induced motion of high-rise buildings. The new hybrid control system utilizes the advantages of both passive and semi-active control systems along with improving the overall performance and eliminating the need for a large power requirement, unlike other proposed hybrid control systems where active and passive systems are combined. Simulation results show that the new hybrid control system is effective in reducing the response of structures significantly under seismic excitations as well as wind loads. It is also demonstrated that the hybrid control system provides increased reliability and maximum operability during normal operations as well as a power or computer failure.

Committee:

Hojjat Adeli (Advisor)

Subjects:

Engineering, Civil

Keywords:

wavelets; structural control; semi-active control; hybrid control; bridge control

Chaudhary, VikrantActive Vibration Control Using Modal Control and Experimental Implementation on Arduino Microcontroller
MS, University of Cincinnati, 2014, Engineering and Applied Science: Mechanical Engineering
Vibration suppression has application in many industries including aerospace for vibration suppression of flexible bodies, automobile for ride comfort though suspensions, and machining devices for precision tooling. Modal control is implemented in modal space instead of local space. As a result the different modes of a system are controlled independently using parallel controllers. The controllers using modal control being low order and simple controllers are easy to implement. The hardware implementation of the closed loop control is expensive which makes it difficult to study the control theories experimentally for academic purposes. In this thesis, the discrete modal filters are reviewed. An analytical method of modal coordinate extraction from physical response data is studied. This method is validated experimentally on an aluminum beam. A mathematical model for a velocity feedback control of a single mode for a multiple input multiple output system is developed and simulated on MATLAB platform. A low cost closed loop hardware based on Arduino microcontroller is developed for experimental implementation of the control theory. An external ADC and DAC are coupled with the Arduino. The controller is programmed based on the functions developed in C++ language.

Committee:

David Thompson, Ph.D. (Committee Chair); Randall Allemang, Ph.D. (Committee Member); J. Kim, Ph.D. (Committee Member)

Subjects:

Mechanics

Keywords:

Active Vibration Control;Modal Control;Discrete Modal Filters;Arduino;Feedback Control Experiment;Collocated Control

Chang, Chin-YaoHierarchical Control of Inverter-Based Microgrids
Doctor of Philosophy, The Ohio State University, 2016, Electrical and Computer Engineering
Electric power grid is experiencing a major paradigm shift toward a more reliable, efficient, and environmentally friendly grid. The concept of microgrid is introduced to integrate distributed renewable generation in proximity to demands for both environmental and power-efficient promises. A microgrid can be disconnected, or "islanded", from the main grid and operates on its own, providing energy to remote areas or during faults of the main grid for better reliability. Islanded microgrids inherit several different properties from traditional power grids, including uncertain and limited generation, mixed R/X ratio lines, and lack of power inertia from synchronous generators. Those properties pose new challenges for the stable operation of islanded microgrids. The dissertation is dedicated to addressing the control challenges of islanded microgrids. The contribution is twofolds. First, we propose a polynomial time optimal power flow (OPF) solver which finds an optimal operating point for the inverters of the distributed energy resources. The proposed algorithm can account for the cost functions on the reactive generation that are common in microgrids. It also brings new understanding on the conjectures of exact semidefinite programming (SDP) convex relaxation on the OPF problem. Furthermore, we show that without the load over-satisfaction assumption usually seen in the literature, a near global optimum can be found for the OPF problem with arbitrary convex quadratic cost functions. The results are important to both microgrids and the classical OPF problem. Our second major contribution is developing a novel distributed controller that addresses the control challenges originated from limited generation, mixed R/X ratio lines, and lack of power inertia properties of islanded microgrids. The proposed controller can ensure proportional active and reactive power sharing and frequency synchronization while respecting the voltage constraints. Variances of the distributed controller are proposed to further relax the communication infrastructure requirements or add compatibility between the real time distributed controller and the OPF solution. An important feature of the proposed OPF solver and the distributed controller is that they can be applied to mesh microgrids with mixed R/X ratio lines. Both the OPF algorithms and the distributed controller are shown effective through simulation studies.

Committee:

Wei Zhang (Advisor); Kevin Passino (Committee Member); Andrea Serrani (Committee Member); Krishnaswamy Srinivasan (Other)

Subjects:

Electrical Engineering; Mechanical Engineering

Keywords:

Distributed control, droop control, hierarchical control, microgrid control, optimal power flow problem, semidefinite programming convex relaxation, near global optimum algorithm

Velasquez Garrido, Jose JFuzzy Model Reference Learning Control for Smart Lights
Master of Science, The Ohio State University, 2013, Electrical and Computer Engineering
This research is motivated by the world's fast-growing demand for energy savings. Due to the increasing cost of fossil fuels (e.g., oil, coal, natural gas), research has been conducted to effectively reduce the electricity consumption in office buildings by means of employing smart lighting. This thesis investigates the implementation of an adaptive and nonadaptive fuzzy control for a smart light experimental testbed. The objective is to accurately regulate the light level across the experimental testbed to a desired voltage reference value, and to test the performance of the fuzzy controllers under cross-illumination effects, and bulb and sensor failures. As an initial approach, a decentralized (i.e., no communication between controllers) nonadaptive fuzzy controller is implemented and applied to the experimental testbed. This approach is convenient for this type of experimental testbed where a mathematical model of the plant is not available and heuristic information about how to control the system is sufficient. The nonadaptive fuzzy controller, when properly tuned, is able to achieve uniform lighting across the entire testbed floor in most of the tested situations but it fails whenever an on/off light bulb failure is introduced. In order to attain uniform lighting for complex failures, a fuzzy model reference learning controller (i.e., adaptive fuzzy) is developed for the experimental testbed, and this algorithm proves to be able to adapt to uncertainties such as disturbances and failures via a learning mechanism.

Committee:

Kevin M. Passino, Prof. (Advisor); Wei Zhang, Prof. (Committee Member)

Subjects:

Electrical Engineering

Keywords:

adaptive algorithm; adaptive fuzzy control; distributed control; lighting control; fuzzy control; smart lights system

Buffington, Adam GreggIndividual Facets of Effortful Control and Symptoms of General Distress and Depression
Master of Arts, The Ohio State University, 2009, Psychology
The present study explored the relationship between positive and negative reactivity, effortful control (EC), and symptoms of both general distress and depression in a sample of 1242 undergraduate students. Participant responses to self-report questionnaire measures of temperament and emotional symptoms were analyzed using multiple linear regression analyses. EC was divided into three facets of attentional control, inhibitory control, and activation control to examine the different relationships between the individual components of EC and emotional problems. Attentional control and inhibitory control were related to symptoms of general distress and depression that were associated with negative reactivity. There was also evidence that attentional control moderated the association between negative reactivity and symptoms of general distress and depression. Conversely, activation control was related to symptoms specific to depression, which are most strongly related to low positive reactivity. Activation control also moderated the association between positive reactivity and anhedonic symptoms such that low positive reactivity was more weakly related to depressive symptoms at higher levels of activation control. Sex differences were found indicating that men were more likely to report symptoms of depression not related to negative reactivity than women. The results also showed that low activation control was related to more depressive symptoms in men than women. There was evidence of an interactive relationship between Behavioral Inhibition (BIS) and Behavioral Activation (BAS) for general distress such that the at low levels of BIS, low BAS was associated with higher reports of general distress, and at high levels of BIS, reports of general distress were similar for both high and low levels of BAS. There was also an interaction between negative affectivity (NA) and positive affectivity (PA) for symptoms of depression such that the relationship between NA and depressive symptoms was reduced at higher levels of PA.

Committee:

Michael Vasey, Ph.D. (Committee Chair); Julian Thayer, Ph.D. (Committee Member); Jennifer Cheavens, Ph.D. (Committee Member)

Subjects:

Psychology

Keywords:

Effortful Control; Attentional Control; Inhibitory Control; Activation Control; General Distress; Anxiety; Depression

Andrecioli, RicardoGrasped Object Detection for Adaptive Control of a Prosthetic Hand
Master of Science, University of Akron, 2013, Mechanical Engineering
Unfortunately, statistical analyses of amputee data shows an increase of the population with upper limb losses either by trauma or birth congenital defects. Several prosthesis options are commercially available, including electric powered prostheses. A review of surveys for upper limb prosthesis users have indicated improvement opportunities in the prosthesis design as well as improved functionality and controls. After review of literature, a PID sliding mode position controller and an adaptive PID sliding mode controller are presented for a prosthetic hand. The adaptive controller smoothly modulates the gains based on the detected stiffness of the grasped object. Three main control strategies will be compared: PID force control, sliding mode position and hybrid sliding mode force-position controllers. For each control option, an adaptive version will also be tested via benchtop experiments. In order to evaluate the performance of each controller under several grasping circumstances, a special manipulandum was designed to provide variable linear and nonlinear stiffness behavior, then each controller was then evaluated according to an experiment plan. The results from benchtop experiments indicate statistically significant improvements such as improved tracking response and reduced steady state error in the system response when using the adaptive controller for all three control cases considered. When comparing Force versus Position versus Hybrid Force-Position control, the latter when equipped of the adaptation method has presented the best results. Preliminary amputee experiments were also conducted using the adaptive hybrid force-position controller in comparison to the constant gain controller as well as the amputees’ current prostheses for daily use. The results of these experiments show that the adaptive hybrid force-position sliding mode controller enabled the amputees to smoothly handle the manipulandum without breaking it.

Committee:

Erik Engeberg, Dr. (Advisor); Subramaniya Hariharan, Dr. (Committee Member); Jiang Zhe, Dr. (Committee Member)

Subjects:

Biomechanics; Mechanical Engineering

Keywords:

Powered upper limb prosthesis; adaptive control; nonlinear control; robust control; stiffness control; stiffness detection.

Sirin, OmerExternal Control Interface, Dynamic Modeling and Parameter Estimation of a Research Treadmill
Master of Science in Biomedical Engineering, Cleveland State University, 2013, Fenn College of Engineering
Treadmills providing linear continuous movement are used for robotic testing of prostheses in order to study their operating characteristics. However, traditional exercise treadmills are not able to simulate various conditions such as avoiding an obstacle, climbing, descending, reversing direction, or stopping instantly. The focus of this thesis is to examine control algorithms (position, speed and force) for the drive mechanism of a research treadmill to fulfill the gap in the situations described above. The system consists of a power supply, a computer with Matlab, and the treadmill that includes a DC motor, a pulley and belt. Also, an external encoder is installed on the motor to measure the position of the belt. The bond graph method is used to model the system to find the symbolic transfer function. Simultaneously, system identification techniques are used to estimate a numeric transfer function. Some parameters of the model are experimentally measured, and the rest are extracted by matching two transfer functions. Control algorithms such as proportional-integral-derivative and sliding mode are implemented in the system for simulation and real-time operation. The results demonstrate that this system is suitable for producing motion paths that traditional treadmills cannot, and it can handle difficult-to-model situations such as the synchronized movement of the treadmill with a prosthesis-testing robot.

Committee:

Hanz Richter, PhD (Committee Chair); Sridhar Ungarala, PhD (Committee Member); Daniel Simon, PhD (Committee Member)

Subjects:

Biomedical Engineering

Keywords:

Control treadmill, PID control treadmill, SMC control treadmill

Hester, Matthew S.Stable Control of Jumping in a Planar Biped Robot
Master of Science, The Ohio State University, 2009, Mechanical Engineering

The ability to perform high-speed dynamic maneuvers is an important aspect of locomotion for bipedal animals such as humans. Running, jumping, and rapidly changing direction are fundamental dynamic maneuvers that contribute to the adaptability and performance required for bipeds to move through unstructured environments. A number of bipedal robots have been produced to investigate dynamic maneuvers. However, the level of performance demonstrated by biological systems has yet to be fully realized in a biped robot. One limiting factor in achieving comparable performance to animals is the lack of available control strategies that can successfully coordinate dynamic maneuvers. This thesis develops a control strategy for producing vertical jumping in a planar biped robot as a preliminary investigation into dynamic maneuvers. The control strategy was developed using a modular approach to allow adaptation to further dynamic maneuvers and robotic systems.

The control strategy was broken into two functional levels to separately solve the problems of planning and performing the jump maneuver. The jump is performed using a low-level controller, consisting of a state machine for determining the current phase of the jump and motor primitives for executing the joint motions required by the current phase. The motor primitives, described by open- and closed-loop control laws, were defined with numeric control parameters for modifying their performance. The high-level controller performs the task of planning the motion required to achieve the desired jump height. Fuzzy control, an intelligent control approach, was selected for the high-level controller. The fuzzy controller uses heuristic information about the biped system to select appropriate control parameters. This heuristic knowledge was implemented in a training algorithm. The training algorithm uses iterative jumps with error-based feedback to determine the control parameters to be implemented by the fuzzy controller.

The control strategy was developed and validated using a numerical simulation of the experimental biped KURMET. The simulation models the dynamics of the biped system and has demonstrated the ability of the control strategy to produce stable successive jumps with an approximate height of 0.575 m. The control strategy was also implemented on the experimental biped for a simplified case, resulting in stable successive jumps with a range of heights from 0.55 to 0.60 m.

Committee:

James Schmiedeler (Advisor); David Orin (Committee Member); Chia-Hsiang Menq (Committee Member)

Subjects:

Electrical Engineering; Engineering; Mechanical Engineering

Keywords:

biped;robot;KURMET;legged;locomotion;jump;jumping;robotics;fuzzy control;intelligent control;control strategy;

Wanichnukhrox, NakrobReal-time visual servo control of a planar robot
Master of Science (MS), Ohio University, 2003, Mechanical Engineering (Engineering)
Real-time visual servo control of a planar robot.

Committee:

Jae Lew (Advisor)

Subjects:

Engineering, Mechanical

Keywords:

Real-Time Control; Visual Control; Servo Control; Planar Robot

Ranka, TruptiDisturbance Rejection Control for The Green Bank Telescope
Doctor of Philosophy, Case Western Reserve University, 2016, EECS - System and Control Engineering
The GBT is a single dish, receiving radio telescope. It is capable of receiving radio waves in the frequency range of 300 MHz to 115 GHz. The off-axis primary reflector of the telescope is 100 meters in diameter. A truss boom (feedarm) extends about 60 meters perpendicular to the primary reflector and is supported at the edge of the reflector. A subreflector is placed at the tip of the feedarm, which directs the focused radio waves from the primary reflector to the radio receivers placed on the feedarm. At high radio frequencies of observation, the uncorrected pointing and tracking errors become limiting factors for making useful scientific observations. The primary reflector and subreflector servo systems need to reduce the pointing and tracking errors due to torque disturbances acting on the system. The overall aim of this research is to redesign the servo control systems such that they are able to give a superior disturbance rejection performance. The 4 contributions of this research are: 1) Verifying the dynamical model of the structure using system identification experiments. 2) The unique reformulation of the extended state observer (ESO) design as a quantitative feedback design problem in frequency domain and splitting the design of the ESO as a feedback observer and a feedforward filter. This formulation gives a more systematic way of designing an ESO as compared to the current technique used for the ESO design. This method is then used to design the ESO based controller for the primary reflector position loop. The ESO based controller provides more than 50% improvement in disturbance rejection in the primary reflector servo loop, as compared to the legacy PID controller. 3) The innovative use of extremum seeking controller (ESC) with a disturbance feedforward signal. We investigate the use of disturbance feedforward with ESC and show that disturbance feedforward improves the speed of the ESC loop by improving the initial condition of the ESC loop and by reducing the magnitude of the error dynamics. 4) The formulation of the subreflector control as an extremum seeking problem, and using the ESC with disturbance feedforward for the subreflector control. This method gives more than 40% improvement in the tracking of a point source against feedarm swaying in wind gusts.

Committee:

Mario Garcia-Sanz (Advisor); Vira Chankong (Committee Member); Sree N. Sreenath (Committee Member); Christos Papachristou (Committee Member)

Subjects:

Astronomy; Electrical Engineering; Systems Science

Keywords:

Robust control, active disturbance rejection control, Extended State Observer, extremum seeking control, large flexible structures, radio telescopes,

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