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A Design Philosophy for Reliable Systems, Including Control

Description: This report develops a framework for a universe of discourse usable by such non-human experts. It is based on the idea that a design has many features of a contract and may be described as a contract between humans and a machine, defining what each must do to attain a goal. Several points are discussed: the use of techniques in analytical redundancy and their place as analogues in administrative control for conventional techniques in physical control; the use of redundant computer systems to protect against hardware faults; the necessity to prove properties of software used in redundant hardware, because software faults are common modes across redundant hardware; and some issues in choosing a programming language for provable control software. Because proof of correctness is costly, it should be used only where necessary. This report concludes that the degree of reliability needed by the plant model used in analytic redundancy protection need not be nearly as reliable as the mechanism to detect discrepancy between plant and model.
Date: April 1984
Creator: Gabriel, John R.
Partner: UNT Libraries Government Documents Department

Networking and Decentralized Control in Layered Networks: a Theoretical Study and Test-bed Development

Description: Layered structures are commonly used in communication systems, but their roles in decentralized control are not understood well. In the first part of this thesis, a theoretical study of consensus (a typical decentralized control task) in layered structures is conducted. The unique graph topology approach permits explicit characterization of consensus performance based on simple graphical characteristics of MLMG structures. In the second part of this thesis, a generic LEGO test-bed to mimic multi-domain communication with layered structures is described. A search-and-rescue scenario is implemented to demonstrate the use of the test-bed.
Date: December 2014
Creator: Sheth, Vardhman Jayeshkumar
Partner: UNT Libraries

Sensor guided control and navigation with intelligent machines. Final technical report

Description: This item constitutes the final report on ''Visionics: An integrated approach to analysis and design of intelligent machines.'' The report discusses dynamical systems approach to problems in robust control of possibly time-varying linear systems, problems in vision and visually guided control, and, finally, applications of these control techniques to intelligent navigation with a mobile platform. Robust design of a controller for a time-varying system essentially deals with the problem of synthesizing a controller that can adapt to sudden changes in the parameters of the plant and can maintain stability. The approach presented is to design a compensator that simultaneously stabilizes each and every possible mode of the plant as the parameters undergo sudden and unexpected changes. Such changes can in fact be detected by a visual sensor and, hence, visually guided control problems are studied as a natural consequence. The problem here is to detect parameters of the plant and maintain st ability in the closed loop using a ccd camera as a sensor. The main result discussed in the report is the role of perspective systems theory that was developed in order to analyze such a detection and control problem. The robust control algorithms and the visually guided control algorithms are applied in the context of a PUMA 560 robot arm control where the goal is to visually locate a moving part on a mobile turntable. Such problems are of paramount importance in manufacturing with a certain lack of structure. Sensor guided control problems are extended to problems in robot navigation using a NOMADIC mobile platform with a ccd and a laser range finder as sensors. The localization and map building problems are studied with the objective of navigation in an unstructured terrain.
Date: March 26, 2001
Creator: Ghosh, Bijoy K.
Partner: UNT Libraries Government Documents Department


Description: In earlier work related to the NSLS-II project we have outlined a control theory approach for the dynamic aperture problem. In particular, an algorithm for the joint optimization of the Lie generator and the working point for the Poincare map. This time we report on how the Lie generator provides guidelines on acceptable magnitudes for e.g. the intrinsic nonlinear effects from insertion devices, and the nonlinear pseudo-invariant from the map normal form can be used to optimize the dynamic aperture. We also show how a polymorphic beam line class can be used to study the parameter dependence and rank conditions for control of optics and dynamic aperture.
Date: June 25, 2007
Partner: UNT Libraries Government Documents Department

An examination of loads and responses of a wind turbine undergoing variable-speed operation

Description: The National Renewable Energy Laboratory has recently developed the ability to predict turbine loads and responses for machines undergoing variable-speed operation. The wind industry has debated the potential benefits of operating wind turbine sat variable speeds for some time. Turbine system dynamic responses (structural response, resonance, and component interactions) are an important consideration for variable-speed operation of wind turbines. The authors have implemented simple, variable-speed control algorithms for both the FAST and ADAMS dynamics codes. The control algorithm is a simple one, allowing the turbine to track the optimum power coefficient (C{sub p}). The objective of this paper is to show turbine loads and responses for a particular two-bladed, teetering-hub, downwind turbine undergoing variable-speed operation. The authors examined the response of the machine to various turbulent wind inflow conditions. In addition, they compare the structural responses under fixed-speed and variable-speed operation. For this paper, they restrict their comparisons to those wind-speed ranges for which limiting power by some additional control strategy (blade pitch or aileron control, for example) is not necessary. The objective here is to develop a basic understanding of the differences in loads and responses between the fixed-speed and variable-speed operation of this wind turbine configuration.
Date: November 1, 1996
Creator: Wright, A.D.; Buhl, M.L. Jr. & Bir, G.S.
Partner: UNT Libraries Government Documents Department

A review of a method for dynamic load distribution, dynamical modeling, and explicit internal force control when two manipulators mutually lift and transport a rigid body object

Description: The paper reviews a method for modeling and controlling two serial link manipulators which mutually lift and transport a rigid body object in a three dimensional workspace. A new vector variable is introduced which parameterizes the internal contact force controlled degrees of freedom. A technique for dynamically distributing the payload between the manipulators is suggested which yields a family of solutions for the contact forces and torques the manipulators impart to the object. A set of rigid body kinematic constraints which restrict the values of the joint velocities of both manipulators is derived. A rigid body dynamical model for the closed chain system is first developed in the joint space. The model is obtained by generalizing the previous methods for deriving the model. The joint velocity and acceleration variables in the model are expressed in terms of independent pseudovariables. The pseudospace model is transformed to obtain reduced order equations of motion and a separate set of equations governing the internal components of the contact forces and torques. A theoretic control architecture is suggested which explicitly decouples the two sets of equations comprising the model. The controller enables the designer to develop independent, non-interacting control laws for the position control and internal force control of the system.
Date: April 20, 1997
Creator: Unseren, M.A.
Partner: UNT Libraries Government Documents Department

Digital signal processing control of induction machine`s torque and stator flux utilizing the direct stator flux field orientation method

Description: This paper presents a review of the Direct Stator Flux Field Orientation control method. This method can be used to control an induction motor`s torque and flux directly and is the application of interest for this thesis. This control method is implemented without the traditional feedback loops and associated hardware. Predictions are made, by mathematical calculations, of the stator voltage vector. The voltage vector is determined twice a switching period. The switching period is fixed throughout the analysis. The three phase inverter duty cycle necessary to control the torque and flux of the induction machine is determined by the voltage space vector Pulse Width Modulation (PWM) technique. Transient performance of either the flux or torque requires an alternate modulation scheme which is also addressed in this thesis. A block diagram of this closed loop system is provided. 22 figs., 7 tabs.
Date: April 1, 1997
Creator: Seiz, J.B.
Partner: UNT Libraries Government Documents Department

Modeling and control of a hydraulically actuated flexible-prismatic link robot

Description: Most of the research related to flexible link manipulators to date has focused on single link, fixed length, single plane of vibration test beds. In addition, actuation has been predominantly based upon electromagnetic motors. Ironically, these elements are rarely found in the existing industrial long reach systems. This manuscript describes a new hydraulically actuated, long reach manipulator with a flexible prismatic link at Oak Ridge National Laboratory (ORNL). Focus is directed towards both modeling and control of hydraulic actuators as well as flexible links that have variable natural frequencies.
Date: December 1996
Creator: Love, Lonnie; Kress, Reid & Jansen, John
Partner: UNT Libraries Government Documents Department

Control mechanisms for a nonlinear model of international relations

Description: Some issues of control in complex dynamical systems are considered. The authors discuss two control mechanisms, namely: a short range, reactive control based on the chaos control idea and a long-term strategic control based on an optimal control algorithm. They apply these control ideas to simple examples in a discrete nonlinear model of a multi-nation arms race.
Date: July 15, 1997
Creator: Pentek, A.; Kadtke, J.; Lenhart, S. & Protopopescu, V.
Partner: UNT Libraries Government Documents Department

A Modular Approach to Redundant Robot Control

Description: This paper describes a modular approach for computing redundant robot kinematics. First some conventional redundant control methods are presented and shown to be `passive control laws`, i.e. they can be represented by a network consisting of passive elements. These networks are then put into modular form by applying scattering operator techniques. Additional subnetwork modules can then be added to further shape the motion. Modules for obstacle detection, joint limit avoidance, proximity sensing, and for imposing nonlinear velocity constraints are presented. The resulting redundant robot control system is modular, flexible and robust.
Date: December 1, 1997
Creator: Anderson, R.J.
Partner: UNT Libraries Government Documents Department

The mechanics of redundantly-driven robotic systems. Final report, September 1988--December 1995

Description: The objectives of this research are to develop systematic methodologies for the creation of multi-degree-of-freedom mechanisms and to gain better understanding of the kinematics, dynamics and control of such devices. The following three inter-related subjects have been studied: (1) tendon-driven manipulators, (2) geared robotic mechanisms, and (3) automotive transmission mechanisms. The main results of this study are summarized.
Date: April 1, 1996
Creator: Tsai, L.W.
Partner: UNT Libraries Government Documents Department

An improved method for calculating self-motion coordinates for redundant manipulators

Description: For a redundant manipulator, the objective of redundancy resolution is to follow a specified path in Cartesian space and simultaneously perform another task (for example, maximize an objective function or avoid obstacles) at every point along the path. The conventional methods have several drawbacks: a new function must be defined for each task, the extended Jacobian can be singular, closed cycles in Cartesian space may not yield closed cycles in joint space, and the objective is point-wise redundancy resolution (to determine a single point in joint space for each point in Cartesian space). The author divides the redundancy resolution problem into two parts: (1) calculate self-motion coordinates for all possible positions of a manipulator at each point along a Cartesian path and (2) determination of optimal self-motion coordinates that maximize an objective function along the path. This paper will discuss the first part of the problem. The path-wise approach overcomes all of the drawbacks of conventional redundancy resolution methods: no need to define a new function for each task, extended Jacobian cannot be singular, and closed cycles in extended Cartesian space will yield closed cycles in joint space.
Date: April 1, 1997
Creator: Reister, D.B.
Partner: UNT Libraries Government Documents Department

Prospects for chaos control of machine tool chatter

Description: The authors analyze the nonlinear tool-part dynamics during turning of stainless steel in the nonchatter and chatter regimes, toward the ultimate objective of chatter control. Their previous work analyzed tool acceleration in three dimensions at four spindle speeds. In the present work, the authors analyze the machining power and obtain nonlinear measures of this power. They also calculate the cycle-to-cycle energy for the turning process. Return maps for power cycle times do not reveal fixed points or (un)stable manifolds. Energy return maps do display stable and unstable directions (manifolds) to and from an unstable period-1 orbit, which is the dominant periodicity. Both nonchatter and chatter dynamics have the unusual feature of arriving at the unstable period-1 fixed point and departing from that fixed point of the energy return map in a single step. This unusual feature makes chaos maintenance, based on the well-known Ott-Grebogi-Yorke scheme, a very difficult option for chatter suppression. Alternative control schemes, such as synchronization of the tool-part motion to prerecorded nonchatter dynamics or dynamically damping the period-1 motion, are briefly discussed.
Date: June 1, 1998
Creator: Hively, L.M.; Protopopescu, V.A.; Clapp, N.E. & Daw, C.S.
Partner: UNT Libraries Government Documents Department

Course of Action Analysis within an Effects-Based Operational Context

Description: This article summarizes information related to the automated course of action (COA) development effort. The information contained in this document puts the COA effort into an operational perspective that addresses command and control theory, as well as touching on the military planning concept known as effects-based operations. The sections relating to the COA effort detail the rationale behind the functional models developed and identify technologies that could support the process functions. The functional models include a section related to adversarial modeling, which adds a dynamic to the COA process that is missing in current combat simulations. The information contained in this article lays the foundation for building a unique analytic capability.
Date: November 1, 2001
Partner: UNT Libraries Government Documents Department

Cooperative motion control for multi-target observation

Description: An important issue that arises in the automation of many security, surveillance, and reconnaissance tasks is that of monitoring (or observing) the movements of targets navigating in a bounded area of interest. A key research issue in these problems is that of sensor placement--determining where sensors should be located to maintain the targets in view. In complex applications involving limited-range sensors, the use of multiple sensors dynamically moving over time is required. In this paper, the author investigates the use of a cooperative team of autonomous sensor-based robots for the observation of multiple moving targets. The focus is primarily on developing the distributed control strategies that allow the robot team to attempt to minimize the total time in which targets escape observation by some robot team member in the area of interest. This paper first formalizes the problem and discusses related work. The author then presents a distributed approximate approach to solving this problem that combines low-level multi-robot control with higher-level reasoning control based on the ALLIANCE formalism. The effectiveness of the approach is analyzed by comparing it to three other feasible algorithms for cooperative control, showing the superiority of the approach for a large class of problems.
Date: August 1, 1997
Creator: Parker, L.E.
Partner: UNT Libraries Government Documents Department

Investigating a reliable covariance control scheme for MDOF systems

Description: The authors attempt to extend their previous efforts towards a reliable control scheme that guarantees a specified degree of reliability for civil engineering structures. Herein, a two degree of freedom system is examined. Covariance control techniques are explored to design a compensator that will provide optimal closed loop performance, while satisfying a constraint on system reliability. It was found for the system under examination that a stable control does not exist that also meets the target reliability level. Alternate formulations continue to be investigated.
Date: June 1, 1998
Creator: Field, R.V. Jr. & Bergman, L.A.
Partner: UNT Libraries Government Documents Department

Wind turbine control system modeling capabilities

Description: At the National Renewable Energy Laboratory`s (NREL`s) National Wind Technology Center the authors are continuing to make progress in their ability to model complete wind turbine systems. An ADAMS{reg_sign} model of the NREL variable speed test bed turbine was developed to determine whether wind turbine control systems could be simulated and to investigate other control strategies for this turbine. Model simulations are compared with data from the operating turbine using the current mode of operation. In general, the simulations show good agreement with test data. Having established confidence in their ability to model the physical machine, the authors evaluated two other control methods. The methods studied are a generalized predictive control method and a bias estimation method. Simulation results using these methods are compared to simulation results of the current mode of operation of the turbine.
Date: April 1, 1998
Creator: Pierce, K. & Fingersh, L.J.
Partner: UNT Libraries Government Documents Department

Neighboring extremal optimal control design including model mismatch errors

Description: The mismatch control technique that is used to simplify model equations of motion in order to determine analytic optimal control laws is extended using neighboring extremal theory. The first variation optimal control equations are linearized about the extremal path to account for perturbations in the initial state and the final constraint manifold. A numerical example demonstrates that the tuning procedure inherent in the mismatch control method increases the performance of the controls to the level of a numerically-determined piecewise-linear controller.
Date: November 1, 1994
Creator: Kim, T.J. & Hull, D.G.
Partner: UNT Libraries Government Documents Department

The Industrial Representative's Perception of the Impact of Managerial Control Systems on Performance

Description: The objective of this study was to examine whether the factors which constitute the manufacturer/industrial-representative relationship, influence performance as predicted by control theory. In addition, the study evaluated the contribution of selected demographic factors such as size of the firm, and the representative's experience, on performance.
Date: August 1995
Creator: Dunipace, Richard A. (Richard Alan)
Partner: UNT Libraries

Understanding How Jurors Award Civil Damages: A Test of Affect Control Theory

Description: This dissertation examines predictors of juror-determined damage awards among 377 juror eligible mock jurors. Citizens reporting for jury duty in a large metropolitan county on five days when the study was conducted were invited to participate. Scenarios were created that varied both case facts and witness emotion during trial testimony. Results indicate that Affect Control Theory can be applied to the situation of juror-determined damage awards and is helpful in scientifically explaining some of the variation of both compensatory and punitive damage awards.
Date: August 2004
Creator: McDonald, Emily
Partner: UNT Libraries

Effects of Control Theory Training Upon Self-Concept and Locus of Control Among Selected University Freshmen

Description: This study examined the effects of Control Theory training upon self-concept and locus of control among students enrolled in the Provisional Admission Program (PAP) at the University of Texas at Arlington. Twenty-nine students randomly assigned to treatment or placebo control groups took the Coppersmith Self-Esteem Inventory (CSSEI-A) and the Adult Nowicki-Strickland Internal-External Locus of Control Scale (ANSIE) as pre- and posttests. Participants in the placebo control group attended their regular educational program for the same amount of time given to the treatment group. No significant differences were found on the Analysis of Covariance for CSSEIā€”A or ANSIE scores following the training period. CSSEI-A and ANSIE scores were elevated, indicating that PAP students think of themselves internally as do other college students, regardless of their SAT scores. The results of this study indicate that Control Theory training is insignificantly effective in producing changes in the self-concept and locus of control among PAP students. Control Theory research may need to be carried out with a smaller group size, use larger samples, provide more time to address the issues specific to PAP student needs, include a stronger counseling emphasis to meet their needs, use more sensitive instruments to detect such changes, and allow more time for the learning to occur before the administration of the posttest.
Date: August 1987
Creator: Smadi, Ahmad Abdel-Majid
Partner: UNT Libraries

NSLS-II Control of Dynamic Aperture

Description: We have outlined how, by an intuitive approach, the on- and off-momentum dynamic aperture for a synchrotron light source can be estimated from a nonlinear system of algebraic equations for the sextupole/multipole strengths. The approach has only two free parameters: the relative weight for resonance vs. tune shift terms and the tune footprint for stable trajectories in a modern third generation synchrotron light source. In other words, we have established a control theory approach for the medium term (10{sup 3} turns) stability for a dynamic system described by a nonlinear system of ordinary differential equations. Equipped with a predictive, quantitative model for stability, we have then evaluated how to improve the control of the dynamics by analyzing and modifying the properties of the corresponding algebraic system. In particular, by changing the number- and characteristics of the parameters, i.e., we have not evaluated how the underlying (linear) optics could be improved. We have also validated our conjectures by numerical simulations with a realistic model. Presumably, our conclusions, summarized in Section 1.0, are a direct result of the presented analysis and observations.
Date: October 31, 2008
Creator: Bengtsson,J.
Partner: UNT Libraries Government Documents Department

A two-timescale approach to nonlinear Model Predictive Control

Description: Model Predictive Control (MPC) schemes generate controls by using a model to predict the plant`s response to various control strategies. A problem arises when the underlying model is obtained by fitting a general nonlinear function, such as a neural network, to data: an exorbitant amount of data may be required to obtain accurate enough predictions. We describe a means of avoiding this problem that involves a simplified plant model which bases its predictions on averages of past control inputs. This model operates on a timescale slower than- the rate at which the controls are updated and the plant outputs are sampled. Not only does this technique give better closed-loop performance from the same amount of open-loop data, but it requires far less on-line computation as well. We illustrate the usefulness of this two-timescale approach by applying it to a simulated exothermic continuously stirred tank reactor with jacket dynamics.
Date: October 1, 1994
Creator: Buescher, K.L. & Baum, C.C.
Partner: UNT Libraries Government Documents Department

H{sub {infinity}} control of chatter in a milling machine

Description: In this paper, preliminary results on the use of active chatter control in a new type of milling machine is presented. It is expected that this machine will cut metal at twice the rate of conventional machines without an appreciable increase in cost. Performance enhancements are achieved by the integration of active feedback control into an existing machine structure. To reduce computational burden, decoupled control is proposed. Extensive simulations have shown that significant performance enhancements are achievable.
Date: May 1, 1997
Creator: Kwan, C.M.; Xu, H.; Lin, C.; Haynes, L.; Dohner, J.; Regelbrugge, M. et al.
Partner: UNT Libraries Government Documents Department