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Althaus, Joseph H.An Embedded Nonlinear Control Implementation for a Hovering Small Unmanned Aerial System
Master of Science (MS), Ohio University, 2010, Electrical Engineering (Engineering and Technology)
This thesis presents the design, development, and experimental verification of an embedded vehicle controller applied to a hovering small unmanned aerial system dubbed the UFO. The effort demonstrated the feasibility of implementation of advanced nonlinear controller designs in embedded hardware to achieve increased system performance. Furthermore, it was shown that the controller implementation was not penalized due to size, weight, and power build-up typically associated with vehicles in this class. Performance was verified experimentally through simulation case studies that subjected the vehicle and embedded controller to various real-world considerations. Finally, justification of approach occurred through analysis of the experimental results.

Committee:

J. Jim Zhu (Advisor)

Subjects:

Electrical Engineering; Engineering

Keywords:

VTOL aircraft; embedded systems; nonlinear control; flight controller; trajectory linearization

Liu, YongNEURAL ADAPTIVE NONLINEAR TRACKING USING TRAJECTORY LINEARIZATION
Doctor of Philosophy (PhD), Ohio University, 2007, Electrical Engineering & Computer Science (Engineering and Technology)

Advanced nonlinear control design methods usually depend on an analytical plant model, which in many practical applications, is often inaccurate or unavailable. Neural networks are a powerful tool to enhance a dynamic model if one is available but inaccurate, or to build a system dynamic model from experimental data. Trajectory linearization control (TLC) is a nonlinear control design method, which combines nonlinear dynamic inversion and linear time-varying (LTV) feedback stabilization to achieve robust tracking control for a broad class of nonlinear dynamic systems. In this dissertation, the research goal is to develop theories and methodologies to improve the understanding and applicability of TLC for inaccurate or lack of dynamic models by using neural networks. To this end, the following research objectives have been achieved. First, rigorous stability robustness analyses of TLC subject to the regular perturbation and singular perturbation are established. Second, a continuous-time nonlinear system identification method using neural network is developed. Third, a neural network trajectory linearization control (NNTLC) design procedure with stability analysis is proposed. Fourth, an adaptive neural network trajectory linearization control (ANNTLC) scheme is presented, in which the neural network control compensates for the system uncertainty adaptively. Illustrative examples of nonlinear applications of TLC, NNTLC and ANNTLC are also presented.

Committee:

J. Zhu (Advisor)

Keywords:

Nonlinear Control; Neural Network; Adaptive Control; Trajectory Linearization Control; System Identification

Terupally, Chandrakanth ReddyTRAJECTORY TRACKING CONTROL AND STAIR CLIMBING STABILIZATION OF A SKID–STEERED MOBILE ROBOT
Master of Science (MS), Ohio University, 2006, Electrical Engineering & Computer Science (Engineering and Technology)

This thesis presents derivation of a trajectory tracking and stair climbing stabilization controller for a 4x4 skid-steered wheeled mobile robot (SSWR). The robot vehicle is a sturdy platform actuated by DC motors capable of traversing difficult terrain. For trajectory tracking, an essential capability for autonomous operation, a reliable and robust controller is needed. In addition, as the vehicle is unstable with manual control while climbing stairs, the controller is required to stabilise it during stair/ramp climb.

The robot vehicle is modelled with six degrees of freedom (6DOF) rigid body equations and an efficient control algorithm, called Trajectory Linearisation Control (TLC), is used to tackle the challenges posed by nonlinearities of the model. In TLC, state dynamics are linearised along the trajectory being tracked and PI control is used to stabilise tracking error dynamics. Kinematics and dynamics are controlled individually using feedback loops, where the former constitutes the outermost loop.

The main contribution of this work is analysis of 6DOF physical model and a consolidated simple controller for planar tracking and stair climbing stabilization for an SSWR. Simulation results promise that a stable climb on 20° steep staircase is possible with current vehicle configuration. Monte Carlo simulations prove that the controller is robust to realistic dispersions of frictional and physical parameters. Effects of perturbations in these parameters have been studied and improvements in mechanical design are suggested.

Committee:

Jianchao Zhu (Advisor)

Keywords:

Trajectory tracking; nonlinear control; trajectory linearisation control; stair climbing; skid-steered mobile robot

Nemati, AlirezaDesigning, Modeling and Control of a Tilting Rotor Quadcopter
PhD, University of Cincinnati, 2016, Engineering and Applied Science: Electrical Engineering
The aim of the present work is to model, design, control, fabricate and experimentally study quadcopter with tilting propellers. A tilting quadcopter is an aerial vehicle whose rotors can tilt along axes perpendicular to their respective axes of rotation. The tilting rotor quadcopter provides the added advantage in terms of additional stable configurations, made possible by additional actuated controls, as compared to a traditional quadcopter without titling rotors. The tilting rotor quadcopter design is accomplished by using an additional motor for each rotor that enables the rotor to rotate along the axis of the quadcopter arm. Conventional quadcopters, due to limitation in mobility, belong to a class of underactuated robots which cannot achieve any arbitrary desired state or configuration. For example, the vehicle cannot hover at a defined point at a tilted angle. It needs to be completely horizontal in order to hover. An attempt to achieve any pitch or roll angle would result in forward (pitch) motion or lateral (roll) motion. This proposed tilting rotor concept turns the traditional quadcopter into an over-actuated flying vehicle allowing us to have complete control over its position and orientation. In this work, a dynamic model of the tilting rotor quadcopter vehicle is derived for flying and hovering modes. The model includes the relationship between vehicle orientation angles and rotor tilt-angles. Furthermore, linear and nonlinear controllers have been designed to achieve the hovering and navigation capability while having any desired pitch and/or roll orientation. In the linear approach, the four independent speeds of the propellers and their rotations about the axes of quadcopter arms have been considered as inputs. In order to start tracking a desired trajectory, first, hovering from the initial starting point is needed. Then, the orientation of the vehicle to the desired pitch or roll angle is obtained. Subsequently, any further change in pitch or roll angles, obtained using a linear controller, result in motion of the quadcopter along the desired trajectory. The dissertation then presents a nonlinear strategy for controlling the motion of the quadcopter. The overall control architecture is divided into two sub-controllers. The first controller is based on the feedback linearization control derived from the dynamic model of the tilting quadcopter. This controls the pitch, roll, and yaw motions required for movement along an arbitrary trajectory in space. The second controller is based on two Proportional Derivative (PD) controllers which are used to control the tilting of the quadcopter independently along the pitch and the yaw directions respectively. The overall control enables the quadcopter to combine tilting and movement along a desired trajectory simultaneously. Furthermore, the stability and control of tilting-rotor quadcopter is presented upon failure of one propeller during flight. On failure of one propeller, the quadcopter has a tendency of spinning about the primary axis fixed to the vehicle as an outcome of the asymmetry about the yaw axis. The tilting-rotor configuration is an over-actuated form of a traditional quadcopter and it is capable of handling a propeller failure, thus making it robust in one propeller failure during the flight. The dynamics of the vehicle once the failure accrued is derived and a controller is designed to achieve hovering and navigation capability. The dynamic model and the controller of the vehicle were verified with the help of numerical studies for diff erent flight scenarios as well as failure mode. Subsequently, two diff erent models of the vehicle were designed, fabricated and tested. Experimental results have validated the dynamical modeling and the flight controllers.

Committee:

Manish Kumar, Ph.D. (Committee Chair); Ali Minai, Ph.D. (Committee Chair); Raj Bhatnagar, Ph.D. (Committee Member); Kelly Cohen, Ph.D. (Committee Member); Rui Dai, Ph.D. (Committee Member)

Subjects:

Electrical Engineering

Keywords:

UAV;Tilt-Rotor Quadcopter;Nonlinear Control;Modeling

Muenst, GerhardMass movement mechanism for nonlinear, robust and adaptive control of flexible structures
Master of Science (MS), Ohio University, 2001, Electrical Engineering & Computer Science (Engineering and Technology)
Mass movement mechanism for nonlinear, robust and adaptive control of flexible structures

Committee:

Dennis Irwin (Advisor)

Keywords:

Mass Movement Mechanism; Nonlinear Control; Robust Control; Adaptive Control; Flexible Structures

Shakiba-Herfeh, MohammadModeling and Nonlinear Control of a 6-DOF Hypersonic Vehicle
Doctor of Philosophy, The Ohio State University, 2015, Electrical and Computer Engineering
In the past two decades, there has been a renewed and sustained effort devoted to modeling the dynamics of air-breathing hypersonic vehicles, for both simulation and control design purposes. The highly nonlinear characteristics of flight dynamics in hypersonic regimes and the consequent significance variability of the response with the operating conditions requires the development of innovative flight control solutions, hence the development of suitable model of the vehicle dynamics that are amenable to design, validation and rapid calibration of control algorithms. In this dissertation, a control-oriented and a simulation model of a generic hypersonic vehicle were derived to support the design and calibration of model-based flight controllers. A nonlinear robust adaptive controller was developed on the basis of the control-oriented model, that was shown to provide stable trajectory tracking in higher fidelity computer simulations. The first stage of this research was the development of a control design model (CDM) for the 6-degree-of-freedom dynamics of an air-breathing hypersonic aircraft based on an available high-fidelity first principle model. A method that incorporates the theory of compressible fluid dynamics and system identification methods, was proposed and implemented. The development of the CDM is based on curve fit approximation of the forces and moments acting on the vehicle, making the model suitable for control design. Kriging and Least Squares methods were used to find the most appropriate curve-fitted model of the aerodynamic forces for both the control design and the control simulation models. It was shown that the 6-DOF model can be both categorized as an under-actuated mechanical system, as well as an over-actuated system with respect to a chosen in- put/output pair of interest. An important contribution of this work is the development of a nonlinear adaptive controller for the 6-DOF control design model. The controller was endowed with a modular structure, comprised of an adaptive inner-loop attitude controller and a robust nonlinear outer-loop controller of fixed structure. The purpose of the outer- loop controller is to avoid the typical complexity of solutions derived from adaptive backstepping methods. A noticeable feature of the outer-loop controller is the presence of an internal model unit that generates the reference for the angle-of-attack, in spite of parametric model uncertainty. Airspeed, lateral velocity, vehicle’s heading and altitude were considered as regulated outputs of the system. Simulation results on the control simulation model show the effectiveness of the developed controller in spite of significant variation in the flight parameters.

Committee:

Andrea Serrani (Advisor); Vadim Utkin (Committee Member); Kevin Passino (Committee Member); Can Koksal (Committee Member)

Subjects:

Electrical Engineering

Keywords:

Nonlinear Control; Aerospace; 6DOF; Hypersonic; Control

Paul, PeterPiecewise polynomial system approximation for nonlinear control
Doctor of Philosophy, Case Western Reserve University, 1994, Electrical Engineering
For nonlinear systems which are linear-in-the-control, the differential geometry based control schemes that have recently been developed require that an accurate smooth model of the nonlinear system be available. When the nonlinear dynamics are unknown, or known but in an inappropriate form for differential geometry calculations, difficulties arise. The approximation and control schemes studied here attempt to resolve these difficulties by casting the original problem into a simpler form. Given data from the nonlinear system, its state-space is partitioned into cells, and a polynomial-in-state model is determined for each cell. After identification, the cell models constitute an overall piecewise polynomial system approximation. Feedback linearization techniques are then performed on the approximated cell models. The overall controller is formed by joining the individual cell controllers to form a global nonlinear controller. Both least squares regression and polynomial spline interpolation are examined for the procedures mentioned above. The calculations needed to perform the identification and the feedback linearization control design are shown in a generic form. In addition, the feedback linearization controller derived from spline based identification is shown to converge to a feedback linearization controller designed with perfect kno wledge of the system dynamics as the spline mesh size approaches zero. Using least squares smoothing, the problems of noisy data and data regularization, which are common in spline interpolation schemes, are addressed. The results of simulating these control schemes on various example nonlinear systems show that the resulting controllers' performance approaches that of a standard input-output feedback linearization controller designed with perfect knowledge of the system dynamics.

Committee:

Stephen Phillips (Advisor)

Keywords:

Piecewise polynomial system approximation nonlinear control

Kandil, Ahmed HishamNonlinear control problems with state and input constraints
Doctor of Philosophy, Case Western Reserve University, 1991, Systems and Control Engineering
This dissertation is concerned with constrained control problems and two types of problems are addressed: control problems with smooth state constraints and control problems with state constraints and smooth input constraints. For the control problems with state constraints, the dynamical system with state constraints is converted into another dynamical system of higher dimension with equality constraints on the initial states. For dynamical systems with multiple constraints and/or multiple inputs, the slack variable method is extended to address this case. It is shown that by proper choice of the slack variables, the resulting dynamical system can be reduced to its original order. Also, the application of feedback linearization for the systems which result from applying the slack variable method is examined. It was found that by input-output feedback linearization the order of the resulting dynamical system is reduced to at least its original order. For control problems with state and input constraints, necessary conditions for the existence of a solution are derived. In this case, the smoothness of the state constraint is relaxed. A solution for the minimum time control problem for a second order system in Brunovsky form subject to state and input constraints is presented. Moreover, some collision a voidance problems for robotic manipulators are formulated in the context of a control problem with state and input constraints.

Committee:

Kenneth Loparo (Advisor)

Subjects:

Engineering, System Science

Keywords:

nonlinear control problems state input constraints

Xu, WanNonlinear Control for Cable Robot Systems with Unidirectional Actuation
Master of Science (MS), Ohio University, 2008, Mechanical Engineering (Engineering and Technology)

Cable robots can only pull not push, as the actuation of each cable is unidirectional. Tradition control methods for cable robots often cannot be used. There are many control techniques applied in systems with input torque saturation limits. However, none of these control methods have been used for cable robots. In this study, the researcher applied two nonlinear control methods for cable robot systems and evaluated their simulation performance.

The tracking control (Moreno-Valenzuela, 2006) and the nonlinear anti-windup control (Morabito et al., 2004) are the two nonlinear control methods which are applied to a cable robot model in this study. Both methods were developed for actuator-saturation control for bi-directional serial robot joints. Here they are applied to unidirectional cable robot control. The two control methods were applied on the model of a cable robot. MATLAB is used to implement the controller and to simulate the system performance. The conclusion involves comparing and evaluating the performance of the proposed nonlinear control methods for cable robot systems.

Committee:

Robert L. Williams II, PhD (Committee Chair); Paul Bosscher, PhD (Committee Member); Douglas A. Lawrence, PhD (Committee Member); Chen Liwei, PhD (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

cable robots; nonlinear control

Lai, HaoyuOn the design of nonlinear gain scheduled control systems
Master of Science (MS), Ohio University, 1998, Electrical Engineering & Computer Science (Engineering and Technology)
On the design of nonlinear gain scheduled control systems

Committee:

Douglas Lawrence (Advisor)

Keywords:

Nonlinear Control Systems; Pitch-Axis Missile Autopilot; Linear Feedback Tracking Controllers

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

Fiorentini, LisaNonlinear Adaptive Controller Design For Air-breathing Hypersonic Vehicles
Doctor of Philosophy, The Ohio State University, 2010, Electrical and Computer Engineering
This dissertation presents the design of two nonlinear robust controllers for an air-breathing hypersonic vehicle model capable of providing stable tracking of velocity and altitude (or flight-path angle) reference trajectories. To overcome the analytical intractability of a dynamical model derived from first principles, a simplified control-oriented model is used for control design. The control-oriented model retains the most important features of the model from which it was derived, including the non-minimum phase characteristic of the flight-path angle dynamics and strong couplings between the engine and flight dynamics. The first control design considers as control inputs the fuel equivalence ratio and the elevator and canard deflections. A combination of nonlinear sequential loop-closure and adaptive dynamic inversion has been adopted for the design of a dynamic state-feedback controller. An important contribution given by this work is the complete characterization of the internal dynamics of the model has been derived for Lyapunov-based stability analysis of the closed-loop system, which includes the structural dynamics. The results obtained address the issue of stability robustness with respect to both parametric model uncertainty, which naturally arises in adopting reduced-complexity models for control design, and dynamic perturbations due to the flexible dynamics. In the second control design a first step has been taken in extending those results in the case in which only two control inputs are available, namely the fuel equivalence ratio and the elevator deflection. The extension of these results to this new framework is not trivial since several issues arise. First of all, the vehicle dynamics are characterized by exponentially unstable zero-dynamics when longitudinal velocity and flight-path angle are selected as regulated output. This non-minimum phase behavior arises as a consequence of elevator-to-lift coupling. In the previous design the canard was strategically used to adaptively decouple lift from elevator command, thus rendering the system minimum phase. Moreover, the canard input was also employed to enforce the equilibrium at the desired trim condition and to provide a supplementary stabilizing action. As a result, when this control input is not assumed to be available, the fact that the system needs to be augmented with an integrator (to reconstruct the desired equilibrium) and the non-minimum phase behavior have a strong impact on the control design. In these preliminary results the flexible effects are not taken into account in the stability analysis but are considered as a perturbation and included in the simulation model. The approach considered utilizes a combination of adaptive and robust design methods based on both classical and recently developed nonlinear design tools. As a result, the issue of robustness with respect to parameter uncertainties is addressed also in this control design. Simulation results on the full nonlinear model show the effectiveness of both controllers.

Committee:

Andrea Serrani (Advisor); Stephen Yurkovich (Committee Member); Kevin Passino (Committee Member); Scott Gaudi (Committee Member)

Subjects:

Electrical Engineering

Keywords:

nonlinear control; adaptive control; aircraft control; hypersonic vehicles

MANICKAM, NITHYANONLINEAR AND ADAPTIVE CONTROL OF MODEL HELICOPTER
MS, University of Cincinnati, 2006, Engineering : Electrical Engineering
A helicopter is a complex nonlinear system and also an under actuated system with fewer independent control actuators than degrees of freedom to be controlled, making the control difficult. There is a growing interest in the modeling and control of such systems using nonlinear dynamic models and nonlinear control. Analytical techniques based on Lyapunov theory are then used to design the controller and still the design can become extremely complex. Hence the existing control methods use linearization techniques on the actual nonlinear dynamics of the plant and linear control techniques. The resulting performance may not be satisfactory, especially when the system is subjected to unknown and sudden disturbances. In this thesis, we present a new Nonlinear and Adaptive controller design which uses the actual nonlinear model of the helicopter and not a linearized version. The design methodology basically involves making the combined dynamics of the helicopter and the controller resemble the dynamics of a nonlinear time varying electrical circuit having the required properties using a process similar to reverse engineering. The circuit template in turn is formed from well defined time varying and/or nonlinear electrical elements and using proper interconnections. The kind of elements used and the general form of the dynamics derived will depend upon the application. For example in the helicopter case, the closed loop dynamics of the helicopter and the controller expressed in terms of the error variable should point to a NLTV circuit with only passive elements. For this, the reactive elements should have their relaxation points (the points where the stored energy is zero) at and only at the origin. Also the stored energy should be monotonically increasing. We can bring in any knowledge including the structure that we have about the plant being controlled in enhancing the circuit.

Committee:

Dr. Panapakkam Ramamoorthy (Advisor)

Keywords:

Nonlinear Control; Circuit Dynamics; Helicopter 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

Lounsbury, William PNonlinear Multi-Mode Robust Control For Small Telescopes
Master of Sciences, Case Western Reserve University, 2015, EECS - Electrical Engineering
This paper introduces an innovative robust and nonlinear control design methodology for high-performance motor control in optical telescopes less than one meter in diameter. The dynamics of optical telescopes typically vary according to azimuth and altitude angles, temperature, friction, speed, and acceleration leading to nonlinearities and plant parameter uncertainty. The methodology proposed in this paper combines robust Quantitative Feedback Theory (QFT) techniques, the describing function method, and optimal control with nonlinear switching strategies that achieve simultaneously the best characteristics of a set of very active (fast) robust QFT controllers, very stable (slow) robust QFT controllers, and a pair of controllers designed around system limit cycles for high precision. A general dynamic model and a variety of specifications from several different commercially available amateur Newtonian telescopes are used for the controller design as well as the simulation and validation. It is also proven that the nonlinear/switching controller is stable for any switching strategy and switching velocity, according to described frequency conditions based on common quadratic Lyapunov functions and the circle criterion.

Committee:

Mario Garcia-Sanz, Ph.D (Advisor); Mario Garcia-Sanz, Ph.D (Committee Chair); Francis Merat, Ph.D (Committee Member); Marc Buchner, Ph.D (Committee Member)

Subjects:

Electrical Engineering; Engineering

Keywords:

Quantitative Feedback Theory; Control Engineering; Telescope; Nonlinear Control; Robust 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

Gunbatar, YakupNonlinear Adaptive Control and Guidance for Unstart Recovery for a Generic Hypersonic Vehicle
Doctor of Philosophy, The Ohio State University, 2014, Electrical and Computer Engineering
This work presents the development of an integrated flight controller for a generic model of a hypersonic air-breathing vehicle. The flight control architecture comprises a guidance and trajectory planning module and a nonlinear inner-loop adaptive controller. The emphasis of the controller design is on achieving stable tracking of suitable reference trajectories in the presence of a specific engine fault (inlet unstart), in which sudden and drastic changes in the vehicle aerodynamics and engine performance occur. First, the equations of motion of the vehicle for a rigid body model, taking the rotation of the Earth into account, is provided. Aerodynamic forces and moments and engine data are provided in lookup-table format. This comprehensive model is used for simulations and verification of the control strategies. Then, a simplified control-oriented model is developed for the purpose of control design and stability analysis. The design of the guidance and nonlinear adaptive control algorithms is first carried out on a longitudinal version of the vehicle dynamics. The design is verified in a simulation study aiming at testing the robustness of the inner-loop controller under significant model uncertainty and engine failures. At the same time, the guidance system provides reference trajectories to maximize the vehicle's endurance, which is cast as an optimal control problem. The design is then extended to tackle the significantly more challenging case of the 6-degree-of-freedom (6-DOF) vehicle dynamics. For the full 6-DOF case, the adaptive nonlinear flight controller is tested on more challenging maneuvers, where values of the flight path and bank angles exceed the nominal range defined for the vehicle. Simulation studies show stable operation of the closed-loop system in nominal operating conditions, unstart conditions, and during transition from sustained scramjet propulsion to engine failure mode.

Committee:

Andrea Serrani, Prof. (Advisor); Umit Ozguner, Prof. (Committee Member); Zhang Wei, Prof. (Committee Member)

Subjects:

Aerospace Engineering; Computer Engineering; Electrical Engineering; Engineering

Keywords:

Hypersonic; unstart; adaptive control; nonlinear control; adaptive backstepping; trajectory optimization; optimal; tuning functions; longitudinal; 6-DOF; 3-DOF; Earth rotation; Control design model; coordinated turn; endurance; Equations of motion

Eyabi, Peter BModeling and sensorless control of solenoidal actuator
Doctor of Philosophy, The Ohio State University, 2003, Mechanical Engineering
Electromagnetic actuators (EMA), which incorporate solenoids, are increasingly becoming the actuator of choice in industry lately, due to their ruggedness, low cost, and relative ease of control. Latest applications of solenoid based EMA’s include Electromagnetic Valve Actuation (EMV) systems. This application presents challenges that require the improvement of the dynamic characteristics of the EMA. Some of these problems include, but are not limited to, quiet operation, reduced bounce, less energy consumption, trajectory shaping with a minimum number of measurements, and high actuation speeds. These demands, coupled with the nonlinear dynamics of the EMA, make the use of classical control strategies a less attractive option. A possible attempt to arrive at intermediate solutions to these problems should include some amount of model based robust control strategy. This includes the development of an accurate but simple control based model and a robust digital control strategy. In this study a basic nonlinear model for a solenoidal EMA will be developed, and validated, which will include bounce, leakage inductance and temperature effects. The model is formulated for the linear legion (region before saturation) of the actuator dynamics, but validation will include operation in the saturation region as well. This effectively means that a nonlinear model will be developed that is simple but accurate enough for control, neglecting hysteresis and magnetic saturation. Next, an EMV will be designed and built. A nonlinear model for the EMV will be developed and validated. This model will include secondary nonlinearities like saturation, hysteresis, mutual inductance and bounce. In this study a variable that is easier and cheaper to measure, current, will be measured and the information of the position and velocity variables will be estimated from this measurement. The position estimate will be used for control. This is called Sensorless Control. The control objective is to reduce impact noise and seating velocity. The sliding mode methodology will be used here since it is nonlinear, robust to uncertainties, and easier to design and implement. The estimation and control algorithms will be validated in simulation and experimentally for the EMA and EMV, respectively.

Committee:

Gregory Washington (Advisor)

Keywords:

solenoids; electromagnetic actuator; sensorless control; sliding mode control; electromagnetic valve actuator; nonlinear observer; nonlinear control

Yan, FengjunDiesel Engine Advanced Multi-Mode Combustion Control and Generalized Nonlinear Transient Trajectory Shaping Control Methods
Doctor of Philosophy, The Ohio State University, 2012, Mechanical Engineering

This dissertation addresses the Diesel engine advanced combustion mode switching transient control and the generalized nonlinear non-equilibrium transient trajectory shaping (NETTS) control problem. Control-oriented models for air- and fuel-path loops were systematically introduced. Models and observers for in-cylinder conditions (ICCs) at the crank angle of intake valve closing were proposed such that the sophisticated Diesel engine combustion control can be promoted from the intake manifold level to the in-cylinder level. Temperature signal reconstruction and in-cylinder wall temperature estimation methods were developed to satisfy the transient control requirements and the sophisticated control on auto-ignitions. Singular perturbation control method on dual-loop exhaust gas recirculation (EGR) and air-/fuel- paths coordinating control algorithms were devised and applied in the combustion mode transition controls. Simulations by a high-fidelity 1D GT-Power Diesel engine model and experiments on a fully-instrumented medium-duty Diesel engine test bench were conducted to show the effectiveness of the aforementioned models, observers, and control algorithms.

From a general engineering application viewpoint, the advanced combustion mode switching transient control problem can be generalized into a broader scope of nonlinear system control. Based on this motivation, generalized nonlinear system non-equilibrium transient trajectory shaping (NETTS) problems were addressed. By the proposed trajectory shaping control methods, the transient tracking error trajectories of a class of nonlinear systems can be shaped within the pre-defined boundaries, in terms of constant series, partial time-varying three-stage boundaries, symmetric time-varying boundaries, and asymmetric time-varying boundaries, before arriving at the equilibrium state. Besides the shaping of the transient tracking errors, the input constraints for the NETTS were considered.

Committee:

Junmin Wang, PhD (Advisor); Chia-Hsiang Menq, PhD (Committee Member); Krishnaswamy Srinivasan, PhD (Committee Member); Xiaodong Sun, Ph.D (Committee Member)

Subjects:

Mechanical Engineering

Keywords:

Diesel engine; advanced combustion mode; nonlinear control; estimation

Kasnakoglu, CoskuReduced order modeling, nonlinear analysis and control methods for flow control problems
Doctor of Philosophy, The Ohio State University, 2007, Electrical Engineering
Flow control refers to the ability to manipulate fluid flow so as to achieve a desired change in its behavior, which offers many potential technological benefits, such as reducing fuel costs for vehicles and improving effectiveness of industrial processes. An interesting case of flow control is cavity flow control, which has been the motivation of this study: When air flow passes over a shallow cavity a strong resonance is produced by a natural feedback mechanism, scattering acoustic waves that propagate upstream and reach the shear layer, and developing flow structures. These cause many practical problems including damage and fatigue in landing gears and weapons bays in aircrafts. Presently there is a lack of sufficient mathematical analysis and control design tools for flow control problems. This includes mathematical models that are amenable to control design. Recently reduced-order modeling techniques, such as those based on proper orthogonal decomposition (POD) and Galerkin projection (GP), have come to interest. However, a main issue with these models is that the effect of boundary conditions, which is where the control input is, gets embedded into system coefficients. This results in a form quite different from what one deals with in standard control systems framework, which is a set of ordinary differential equations (ODE) where the input appears as an explicit term. Another issue with the standard POD/GP models is that they do not yield to systems that have any apparent structure in their coefficients. This leaves one with little choice other than to neglect the nonlinearities of the models and employ standard linear control theory based designs. The research presented in this thesis makes an effort at closing the gaps mentioned above by 1) presenting a reduced-order modeling method utilizing a novel technique for input separation on POD/GP models, 2) introducing a technique based on averaging theory and center manifold theory so as to reveal certain structures embedded in the model, and 3) developing nonlinear analysis and control design approaches for the resulting model. The theory is complemented by examples and case studies as appropriate, including the case of cavity flow control.

Committee:

Andrea Serrani (Advisor)

Keywords:

flow control; cavity flow; nonlinear analysis; nonlinear control; proper orthogonal decomposition; Navier-Stokes; POD; Galerkin projection; GP; reduced order modeling; averaging theory; center manifold theory

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.