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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

Phase-Space Reconstruction: a Path Towards the Next Generation of Nonlinear Differential Equation Based Models and Its Implications Towards Non-Uniform Sampling Theory

Description: This paper explores the overlaps between the Control community’s work on System Identification (SysID) and the Physics, Mathematics, Chaos, and Complexity communities’ work on phase-space reconstruction via time-delay embedding. There are numerous overlaps between the goals of each community. Nevertheless, the Controls community can gain new insight as well as some new very powerful tools for SysID from the latest developments within the Physics, Mathematics, Chaos, and Complexity communities. These insights are gained via the work on phase-space reconstruction of non-linear dynamics. New methods for discovering non-linear differential based equations that evolved from embedding operations can shed new light on hybrid-systems theory, Nyquest-Shannon’s Theories, and network based control theory. This paper strives to guide the Controls community towards a closer inspection of the tools and additional insights being developed within the Physics, Mathematics, Chaos, and Complexity communities for discovery of system dynamics, the first step in control system development. The paper introduces the concepts of phase-space reconstruction via time-delay embedding (made famous byWhitney, Takens, and Sauer’s Thoreoms), intergrate-and-fire embedding, and non-linear differential equation discovery based on Perona’s method.
Date: August 1, 2009
Creator: Tolle, Charles R. & Pengitore, Mark
Partner: UNT Libraries Government Documents Department

Experimental development of power reactor advanced controllers

Description: A systematic approach for developing and verifying advanced controllers with potential application to commercial nuclear power plants is suggested. The central idea is to experimentally demonstrate an advanced control concept first on an ultra safe research reactor followed by demonstration on a passively safe experimental power reactor and then finally adopt the technique for improving safety, performance, reliability and operability at commercial facilities. Prior to completing an experimental sequence, the benefits and utility of candidate advanced controllers should be established through theoretical development and simulation testing. The applicability of a robust optimal observer-based state feedback controller design process for improving reactor temperature response for a TRIGA research reactor, Liquid Metal-cooled Reactor (LMR), and a commercial Pressurized Water Reactor (PWR) is presented to illustrate the potential of the proposed experimental development concept.
Date: January 1, 1992
Creator: Edwards, R.M. (Pennsylvania State Univ., University Park, PA (United States). Dept. of Nuclear Engineering); Weng, C.K. (Pennsylvania State Univ., University Park, PA (United States). Dept. of Mechanical Engineering) & Lindsay, R.W. (Argonne National Lab., Idaho Falls, ID (United States))
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

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

Models, controls, and levels of semiotic autonomy

Description: In this paper the authors consider forms of autonomy, forms of semiotic systems, and any necessary relations among them. Levels of autonomy are identified as levels of system identity, from adiabatic closure to disintegration. Forms of autonomy or closure in systems are also recognized, including physical, dynamical, functional, and semiotic. Models and controls are canonical linear and circular (closed) semiotic relations respectively. They conclude that only at higher levels of autonomy do semiotic properties become necessary. In particular, all control systems display at least a minimal degree of semiotic autonomy; and all systems with sufficiently interesting functional autonomy are semiotically related to their environments.
Date: December 1, 1998
Creator: Joslyn, C.
Partner: UNT Libraries Government Documents Department

Reliability-based covariance control design

Description: An extension to classical covariance control methods, introduced by Skelton and co-workers, is proposed specifically for application to the control of civil engineering structures subjected to random dynamic excitations. The covariance structure of the system is developed directly from specification of its reliability via the assumption of independent (Poisson) outcrossings of its stationary response process from a polyhedral safe region. This leads to a set of state covariance controllers, each of which guarantees that the closed-loop system will possess the specified level of reliability. An example civil engineering structure is considered.
Date: March 1, 1997
Creator: Field, R.V. Jr. & Bergman, L.A.
Partner: UNT Libraries Government Documents Department

Multi-robot motion control for cooperative 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 authors investigate the use of a cooperative team of autonomous sensor-based robots for the observation of multiple moving targets. They focus 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 authors then present 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. They analyze the effectiveness of the approach by comparing it to 3 other feasible algorithms for cooperative control, showing the superiority of the approach for a large class of problems.
Date: June 1, 1997
Creator: Parker, L.E.
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

Online high voltage power supply ripple estimation and feedforward in LEDA

Description: The Low Energy Demonstration Accelerator (LEDA) being constructed at Los Alamos National Laboratory will serve as the prototype for the low energy section of Acceleration Production of Tritium (APT) accelerator. This paper addresses the problem of LLRF control system for LEDA. They propose an estimator of the ripple and its time derivative and a control law which is based on PID control and adaptive feedforward of estimated ripple. The control law reduces the effect of the deterministic cathode ripple that is due to high voltage power supply and achieves tracking of desired set points.
Date: June 1, 1999
Creator: Kwon, S.; Regan, A.; Wang, Y.M. & Rohlev, T.
Partner: UNT Libraries Government Documents Department

Feedback linearization application for LLRF control system

Description: The Low Energy Demonstration Accelerator (LEDA) being constructed at Los Alamos National Laboratory will serve as the prototype for the low energy section of Acceleration Production of Tritium (APT) accelerator. This paper addresses the problem of the LLRF control system for LEDA. The authors propose a control law which is based on exact feedback linearization coupled with gain scheduling which reduces the effect of the deterministic klystron cathode voltage ripple that is due to harmonics of the high voltage power supply and achieves tracking of desired set points. Also, they propose an estimator of the ripple and its time derivative and the estimates based feedback linearization controller.
Date: June 1, 1999
Creator: Kwon, S.; Regan, A.; Wang, Y.M. & Rohlev, T.
Partner: UNT Libraries Government Documents Department

Design and experimental evaluation of flexible manipulator control algorithms

Description: Within the Environmental Restoration and Waste Management Program of the US Department of Energy, the remediation of single-shell radioactive waste storage tanks is one of the areas that challenge state-of-the-art equipment and methods. The use of long-reach manipulators is being seriously considered for this task. Because of high payload capacity and high length-to-cross-section ratio requirements, these long-reach manipulator systems are expected to use hydraulic actuators and to exhibit significant structural flexibility. The controller has been designed to compensate for the hydraulic actuator dynamics by using a load-compensated velocity feedforward loop and to increase the bandwidth by using an inner pressure feedback loop. Shaping filter techniques have been applied as feedforward controllers to avoid structural vibrations during operation. Various types of shaping filter methods have been investigated. Among them, a new approach, referred to as a ``feedforward simulation filter`` that uses embedded simulation, has been presented.
Date: April 1, 1995
Creator: Kwon, D.S.; Hwang, D.H.; Babcock, S.M.; Kress, R.L.; Lew, J.Y. & Evans, M.S.
Partner: UNT Libraries Government Documents Department

Magnetic damping for maglev

Description: Magnetic damping is one of the important parameters to control the response and stability of maglev systems. An experimental study is presented to measure the magnetic damping using a direct method. A plate attached to a permanent magnet levitated on a rotating drum was tested to investigate the effect of various parameters on magnetic damping such as conductivity, gap, excitation frequency, and oscillation amplitude. The experimental technique is capable of measuring all magnetic damping coefficients, some of which can not be measured by an indirect method.
Date: December 31, 1994
Creator: Chen, S.S.; Zhu, S.; Cai, Y. & Rote, D.M.
Partner: UNT Libraries Government Documents Department

Solving inverse problems of identification type by optimal control methods

Description: Inverse problems of identification type for nonlinear equations are considered within the framework of optimal control theory. The rigorous solution of any particular problem depends on the functional setting, type of equation, and unknown quantity (or quantities) to be determined. Here the authors present only the general articulations of the formalism. Compared to classical regularization methods (e.g. Tikhonov coupled with optimization schemes), their approach presents several advantages, namely: (i) a systematic procedure to solve inverse problems of identification type; (ii) an explicit expression for the approximations of the solution; and (iii) a convenient numerical solution of these approximations.
Date: June 1, 1997
Creator: Lenhart, S.; Protopopescu, V. & Jiongmin Yong
Partner: UNT Libraries Government Documents Department

Beam bunch feedback

Description: When the electromagnetic fields that are excited by the passage of a bundle of charged particles persist to act upon bunches that follow, then the motions of the bunches are coupled. This action between bunches circulating on a closed orbit can generate growing patterns of bunch excursions. Such growth can often be suppressed by feedback systems that detect the excursion and apply corrective forces to the bunches. To be addressed herein is feedback that acts on motions of the bunch body centers. In addition to being useful for suppressing the spontaneous growth of coupled-bunch motions, such feedback can be used to damp transients in bunches injected into an accelerator or storage ring; for hadrons which lack strong radiation damping, feedback is needed to avoid emittance growth through decoherence. Motions excited by noise in magnetic fields or accelerating rf can also be reduced by using this feedback. Whether the action is on motions that are transverse to the closed orbit or longitudinal, the arrangement is the same. Bunch position is detected by a pickup and that signal is processed and directed to a kicker that may act upon the same bunch or some other portion of the collective beam pattern. Transverse motion is an oscillation with angular frequency {nu}{perpendicular}{omega}{sub o} where {omega}{sub o} is the orbital frequency 2{pi}{line_integral}o. Longitudinal synchrotron oscillation occurs at frequency {omega} {sub s} = {nu}{sub s}{omega}{sub o}. The former is much more rapid, {nu}{perpendicular} being on the order of 10 while {nu}{sub s} is typically about 10{sup minus 1} to 10 {sup minus 2}.
Date: September 1, 1995
Creator: Lambertson, G.
Partner: UNT Libraries Government Documents Department

ALLIANCE: An architecture for fault tolerant, cooperative control of heterogeneous mobile robots

Description: This research addresses the problem of achieving fault tolerant cooperation within small- to medium-sized teams of heterogeneous mobile robots. The author describes a novel behavior-based, fully distributed architecture, called ALLIANCE, that utilizes adaptive action selection to achieve fault tolerant cooperative control in robot missions involving loosely coupled, largely independent tasks. The robots in this architecture possess a variety of high-level functions that they can perform during a mission, and must at all times select an appropriate action based on the requirements of the mission, the activities of other robots, the current environmental conditions, and their own internal states. Since such cooperative teams often work in dynamic and unpredictable environments, the software architecture allows the team members to respond robustly and reliably to unexpected environmental changes and modifications in the robot team that may occur due to mechanical failure, the learning of new skills, or the addition or removal of robots from the team by human intervention. After presenting ALLIANCE, the author describes in detail experimental results of an implementation of this architecture on a team of physical mobile robots performing a cooperative box pushing demonstration. These experiments illustrate the ability of ALLIANCE to achieve adaptive, fault-tolerant cooperative control amidst dynamic changes in the capabilities of the robot team.
Date: February 1, 1995
Creator: Parker, L.E.
Partner: UNT Libraries Government Documents Department

Miniature Autonomous Robotic Vehicle (MARV)

Description: Sandia National Laboratories (SNL) has recently developed a 16 cm{sup 3} (1 in{sup 3}) autonomous robotic vehicle which is capable of tracking a single conducting wire carrying a 96 kHz signal. This vehicle was developed to assess the limiting factors in using commercial technology to build miniature autonomous vehicles. Particular attention was paid to the design of the control system to search out the wire, track it, and recover if the wire was lost. This paper describes the test vehicle and the control analysis. Presented in the paper are the vehicle model, control laws, a stability analysis, simulation studies and experimental results.
Date: December 31, 1996
Creator: Feddema, J.T.; Kwok, K.S.; Driessen, B.J.; Spletzer, B.L. & Weber, T.M.
Partner: UNT Libraries Government Documents Department

SIAM symposium on control problems in industry

Description: This symposium focused on industrial control applications that have benefited from recent mathematical and technological developments. The themes featured included: applications of control techniques in aerospace industry, automotive industry, environmental sciences, manufacturing processes, and petroleum industry; optimal shape design in aerospace applications; optimal design of micro-optics; robust control and H-infinity methods.
Date: December 31, 1994
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

Intelligent decision support technologies for design and manufacturing

Description: For many of today`s complex manufacturing processes, there exists a solid body of knowledge that enables direct simulations of such processes yielding predictions about the final product and process characteristics using finite element or finite difference methods. However, the computational complexities of these simulations are such that they do not lend themselves easily to routine and timely use in optimization and control of manufacturing processes. More recently, neural network-based decision support technologies have been developed which hold the promise of bringing the body of analytical and simulation knowledge closer to the design and optimization processes in manufacturing industries. The paper discusses the application of a holistic approach wherein existing finite element, neural-network, and optical metrology methods are combined to develop a real time tool for optimization and control of the sheet metal stamping process. Significant issues in the development of such a tool and results from its application to a deformation process are discussed.
Date: June 1, 1997
Creator: Zacharia, T.; Allen, J.D.; Ivezic, N. & Ludtka, G.M.
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

Results from the NREL Variable-Speed Test bed

Description: The NREL Variable-Speed Test bed turbine has been used to examine the performance and controllability of a variable-speed, variable-pitch turbine. Control strategies that eliminate drive-train torque fluctuations in high winds have been published before and example data are given here. The energy capture of a variable-speed wind turbine depends in part on its ability to successfully operate at the peak of the C{sub p}-{lambda} curve. The losses associated with the inability of the rotor to stay exactly on top of the curve at all have been found and quantified. New control strategies for improving energy capture in moderate winds are also proposed. The potential exists to improve overall energy capture by 5% or more.
Date: November 1, 1997
Creator: Fingersh, L.J. & Carlin, P.W.
Partner: UNT Libraries Government Documents Department