Browsing by Subject "Control theory"
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Item Adaptation, gyro-ree stabilization, and smooth angular velocity observers for attitude tracking control applications(2014-08) Thakur, Divya, active 21st century; Akella, Maruthi Ram, 1972-This dissertation addresses the problem of rigid-body attitude tracking control under three scenarios of high relevance to many aerospace guidance and control applications: adaptive attitude-tracking control law development for a spacecraft with time-varying inertia parameters, velocity-free attitude stabilization using only vector measurements for feedback, and smooth angular velocity observer design for attitude tracking in the absence of angular velocity measurements. Inertia matrix changes in spacecraft applications often occur due to fuel depletion or mass displacement in a flexible or deployable spacecraft. As such, an adaptive attitude control algorithm that delivers consistent performance when faced with uncertain time-varying inertia parameters is of significant interest. This dissertation presents a novel adaptive control algorithm that directly compensates for inertia variations that occur as either pure functions of the control input, or as functions of time and/or the state. Another important problem considered in this dissertation pertains to rigid-body attitude stabilization of a spacecraft when only a set of inertial sensor measurements are available for feedback. A novel gyro-free attitude stabilization solution is presented that directly utilizes unit vector measurements obtained from inertial sensors without relying on observers to reconstruct the spacecraft's attitude or angular velocity. As the third major contribution of this dissertation, the problem of attitude tracking control in the absence of angular velocity measurements is investigated through angular velocity observer (estimator) design. A new angular velocity observer is presented which is smoothed and ensures asymptotic convergence of the estimation errors irrespective of the initial true states of the spacecraft. The combined implementation of a separately designed proportional-derivative type controller using estimates generated by the observer results in global asymptotic stability of the overall closed-loop tracking error dynamics. Accordingly, a separation-type property is established for the rigid-body attitude dynamics, the first such result to the author's best knowledge, using a smooth (switching-free) observer formulation.Item Adaptive critic designs and their applications(Texas Tech University, 1997-12) Prokhorov, Danil VNOT AVAILABLEItem Algorithms in system identification(Texas Tech University, 1988-08) Shaukat, Aamer SohailA first set of FORTRAN programs was written that generates noisy input output data from a multi-input, multi-output, linear, time-invariant system. A random number generator is used to produce the output noise. The system parameters are identified from the noisy input-output data using an adaptation of the least squares method in the second set of programs. The third set presents a new algorithm for system parameter identification using the concept of the supremal [F, G]-invariant subspace in ker[H], and some results from optimal control theory. Most of the results are calculated and tabulated for a specific two-input, two-output, third order system.Item An investigation of LQG performance measure distributions(Texas Tech University, 1973-05) Erspamer, Michael StephenNot availableItem Characterization of digital phase-locked loops(Texas Tech University, 2003-05) Vepa, Sri Kiran V SPhase-locked loops are a relatively new class of circuits used primarily in communication applications. The capture range of a phase-locked loop is a critical parameter because it trades directly with the loop bandwidth. Different architectures for the phase-locked loop (PLL) have been proposed which can broaden the capture range (1-3]. However, in most of the research, very little emphasis was made on studying the exact dependence of the capture range on the different circuit parameters, which define the individual components of a phase-locked loop. The effect of these parameters, for instance, the W/L ratio of the transistors, can be prominent. This thesis is aimed at designing a circuit for a digital phase locked loop, characterizing the components and discussing a method of estimating the capture range. This circuit can act as a starting point in solving the above mentioned problem. The next step would be to observe the dependence of capture range on circuit parameters.Item Control of distributed parameter systems(Texas Tech University, 1986-12) Tubach-Ley, Wilhelmina BarbaraNot availableItem Ctrl.FRAME : a control-theoretical framework for resource allocation management in engineering(2011-12) Mozano, Ashton; Barber, Suzanne; Graser, ThomasThe Software Life Cycle (SLC) often comprises a complex sequence of processes, each with many subparts where various execution decisions throughout the pipeline can greatly affect the success or failure of a given project. Some of the most important decisions involve the allocation of scarce resources throughout the SLC, which are often based on estimations about future market demand and various extraneous factors of high stochasticity. Despite numerous efforts in standardization, many projects are still highly dependent on the subjective aptitude of individual managers, who may in turn rely on ad hoc techniques rather than standardized and repeatable ones. The results can be unpredictability and undue reliance on specific individuals. This paper considers imposing a mathematical framework on two of the key aspects of SLC: Deciding how to dynamically allocate available resources throughout the development pipeline, and when to stop further work on a given task in light of the associated Return On Investment (ROI) metrics. In so doing, the software development process is modeled as a problem in New Product Development (NPD) Management, which can be approached using control theory and stochastic combinatorial optimization techniques. The paper begins by summarizing some of the previous developments in these fields, and proposes some future research directions for solving complex resource allocation problems under stochastic settings. The outcome is a formal framework that when combined with competent Configuration Management techniques, can rapidly achieve near-optimal solutions at each stage of the SLC in a standardized manner.Item Cumulant control of discrete time linear stochastic systems(Texas Tech University, 1979-05) Parten, Clifford RayTraditionally, feedback regulator control laws for linear stochastic systems have been achieved by minimization of the mathematical expectation of a particular quadratic performance measure. Over the past decade some research efforts have been directed at the generalization of this class of problems to include higher-order statistical indices, involving mean-conditional-cumulants of the quadratic performance measure. However, these efforts, which were made in the continuous time case, have not yielded a complete generalization. In this work such a generalization is achieved. The key question addressed involves enforcement of an "admissibility" constraint on the set of control actions over which optimization is carried out. This constraint assures that the control actions will be physically realizable and determined by feedback control laws. The main result of this work is the discovery of an equivalent optimization problem where the admissibility constraint is not present.Item Examining individual differences as predictors of reinforcement and punishment behaviors within romantic couples dealing with substance use : an application of inconsistent nurturing as control theory(2013-05) Glowacki, Elizabeth Marie; Donovan-Kicken, Erin E.Managing a romantic partner’s substance misuse can be challenging, especially in cases where attempts to show support end up worsening the negative behavior. Understanding what may predict one’s actions towards a partner who smokes or drinks can help to alleviate some of the difficulty associated with these interactions. Therefore, this study was designed to examine how issues of undesirable substance use are managed within college students’ romantic relationships. More specifically, the study applied Inconsistent Nurturing as Control Theory (Le Poire, 1995) to assess the extent to which communication competence, relational uncertainty, perceived network helpfulness, and perceived network hindrance predict the reinforcement and/or punishment of a partner’s smoking or drinking. Results from cross-sectional survey data (N = 270) revealed that a significant, negative relationship existed between perceived network helpfulness and punishment and that there were significant, positive relationships between: perceived network hindrance and punishment, relational uncertainty and reinforcement, and relational uncertainty and punishment. However, there was no evidence indicating that communication competence was correlated with either reinforcement or punishment. Additional findings revealed that individuals reporting on their partners’ drinking, as opposed to their partners’ smoking, were more likely to reinforce the behavior. Men reported on using more reinforcement behaviors than women did and individuals who were in on-again/off-again relationships reported using more punishment than did those in relationships that have not renewed. In addition to examining the communicative behaviors used to address substance misuse, the current study also furthered the development of a scale created for the purposes of quantitatively measuring the constructs of reinforcement and punishment. Implications for studying predictors of reinforcement and punishment strategies are discussed, as is the importance of targeting young adult substance use.Item Feedback system design: the pole placement problem(Texas Tech University, 1982-12) Iyer, AshokNot availableItem Hierarchical systems implementation with microprocessor(Texas Tech University, 1978-05) Chiang, MingNot availableItem Human posture control: preparation gait to avoid slips and falls(Texas Tech University, 2004-05) Park, Woo-HyungThe purpose of the present study was to identify preparation gait patterns for avoiding slips and falls. Six experimental conditions combining two walking speeds and three internal gait models were presented. In order to investigate the initiation time of the preparation gait, subject walking speed was manipulated by using two step frequencies. In order to investigate the effect of a subject's intention and future external condition, the internal gait model was manipulated by combining two adaptation gait styles and two target surface conditions. The hypotheses of this study were that (1) a preparation gait is observable and significantly different from a normal surface gait; (2) a preparation gait pattern is a function of an internal gait model; and (3) a preparation gait is initiated as a function of walking speed. To test the hypotheses, (1) kinetics and kinematics of gait were simulated using a two-link inverted pendulum model applying a system control theory; (2) the simulation results were used to derive specific hypotheses concerning how the preparation gait is generated by each of two adaptation gaits, that is, the walk-over adaptation gait and the slide-over adaptation gait; and (3) kinetic and kinematic data were collected from human subjects to identify the preparation gait. It was found that a preparation gait involves several levels of motor programming. At the level of segment control, the overall motion patterns of segments are consistent regardless of the internal gait model. At the level of coordination control, different coordination patterns were found, corresponding to different internal gait models. Subjects attempted certain initial postures to adapt to a slippery surface, minimizing the foot and shank forward angles and maximizing the thigh and trunk forward angles. To do this, subjects reduced the angular velocity of distal segments more than that of the proximal segments. Subjects also changed the coordination strength of adjacent segments from the distal segments to the proximal segments as balance control became critical. Finally, preparation gait is initiated in the middle of the step cycle prior to contact with a slippery surface: preparation gait was a part of the gait rather than a unique movement.Item Information projections in learning(Texas Tech University, 1999-08) Kirupaharan, NadarajahThis thesis is aimed at discussing the relevance of the theory of reference frames in mathematical psychology in understanding the differences between biological and engineering control systems. As an example, the problem of human posture control is discussed via the use of a simplified model. The head, upper torso, and the upper legs are represented as straight lines with point masses attached to their mid points. The fact that as a child first learns to balance head with his mother's help, then the hip while sitting, and then the knee is taken into account in this representation. If the problem of the control of the head is P1, the head and the upper torso is P2 and everything above the knee is P3, it is contended that the solution of P2 is a natural extension of the solution of P1 and the solution of P3 is a natural extension of the solution of P2. Subsequently each problem is considered individually. At each stage, control laws for torque are written in terms of position, velocity and acceleration variables. Our theory leads to a natural solution which is consistent with everyday observations of how a child masters posture control.Item Linear time-varying systems: Algebraic structure, system properties and control(Texas Tech University, 1987-08) Tai, Heng-mingThe purpose of this dissertation is two-fold. First, a novel algebraic framework for linear continuous-time time-varying systems based on the fractional representation approach is presented (mainly from C14]). The main structure of this realization and control theory is a module of signals aver a skew polynomial ring consisting of time-varying differential polynomials. The realization problem based on the formal Kalman input-output map (as right module homomorphism) is considered. This leads to the Hankel matrix introduced by Kalman (see C35]). It is shown that reachability and observability can be characterized by coprime polynomial factorization conditions. The relation between the formal impulse response and Rosenbrock's system matrix is also closely investigated. Secondly, several systemtheoretic properties such as stabilizability and detectability and their relations for the class of constant rank systems are explored. One of the primary tools used in this development is an improved version of Dolezal's theorem. It is shown that stabilizability (resp. detectability) and asymptotic controllability (resp. asymptotic observability) are equivalent. The concept of open-loop stabilizability is introduced and its relation to the steady state solution of the matrix Riccati equation is examined. It is also shown that four notions of detectability for constant rank systems are eguivalent to each other.Item Local issues in trajectory planning(Texas Tech University, 2002-08) Palamakumbura, RathnamaliThe trajectory planning problem for MIMO linear systems is considered in this work. The problem has received wide interest due to its relevance in aviation, robotics, and biomechanics to name a few. It is naturally formulated in the settingof a constrained ptimization problem where the cost of control is minimized subject to the path constraints related to the time history. The convex nature of the resulting optimization problem enables the use of the method of Lagrange multipliers to solve it. Many authors have considered this problem. However, their work is only with respect to SISO linear systems, where we consider the more general and harder MIMO case. An example is provided to illustrate the results derived.Item Modeling and analysis of hybrid dynamic systems(Texas Tech University, 1996-12) Gotesman, MosheA modeling technique for hybrid dynamics systems, using high-level Petri nets, is presented. A hybrid dynamics system is a continuous dynamics system in which discrete events occur. Modeling of hybrid dynamics systems is difficult since continuous dynamics and discrete event dynamics have entirely different mathematics. The dissertation presents techniques for converting a hybrid dynamics system, represented mathematically or by means of a block diagram into a Petri net. The resulting Petri net. called the Hybrid Dynamics Petri Net (HDPN). captures both the continuous and discrete event phenomena in the system. This provides a single formalism for modeling hybrid dynamics systems. Procedures are also provided for converting a Petri net into a block diagram and into a mathematical representation. Some examples are implemented to demonstrate the capability of the Petri net formalism to correctly model hybrid dynamics systems. The examples demonstrate the modeling power of Petri nets for continuous and hybrid systems, including non-linear systems and MIMO systems.Item Nonlinear control with two complementary Lyapunov function(2016-12) Zelenak, Andrew J.; Landsberger, Sheldon; Pryor, Mitchell; Deshpande, Ashish; Fernandez, Benito; Kautz, DougIf a Lyapunov function is known, a dynamic system can be stabilized. However, computing or selecting a Lyapunov function is often challenging. This dissertation presents a new approach which eliminates this challenge: a simple control Lyapunov function [CLF] is assumed then the algorithm seeks to reduce the value of the Lyapunov function. If the control effort would have no effect at any iteration, the CLF is switched in an attempt to regain control. There is some flexibility in choosing these two complementary CLF’s but they must satisfy a few characteristics. The method is proven to asymptotically stabilize a wide range of nonlinear systems and was tested on an even broader variety in simulation. It was also tested on an industrial robot to provide compliant behavior. The simulated and hardware demonstrations provide a broad perspective on the algorithm’s usefulness and limitations. In comparison to the ubiquitous PID controller, the algorithm’s advantages include enhanced performance, ease of tuning, and extensions to higher-order and/or coupled systems. Those claimed advantages are validated by a test with four engineering students, which validates the controller as a viable option for nonlinear control (even at the undergraduate level). The algorithm’s drawbacks include the necessity of a dynamic model and, when linearization is required, the reliance on a small simulation time step; however, for the motivating application –interactive industrial robotic systems – both requirements were already met. Finally, the developed software was released to the public as part of the Robot Operating System (ROS) and the details of that release are included in this report.Item Item On algebraic aspects of control(Texas Tech University, 1983-12) Bailey, Susan GruenhagenNot availableItem On some aspects of convex optimal control theory(Texas Tech University, 1971-08) Rajaraman, Manjeri KNot available