bluuebunny/crossref_metadata_2025 huggingface dataset:
Computer Evaluation of Controlled Pantographs for Current Collection From Simple Catenary Overhead Equipment at High Speed
Authors: Vinayagalingam T.
Published: July 2009

A digital computer simulation technique is used to study the effects of changing pantograph characteristics upon the quality of current collection from simple catenary overhead equipment at high speed. In particular, the likely benefits to be derived by the use of controlled pantographs are assessed. Pantograph performance is judged on the basis of contact force variation and displacement responses of pantograph and contact wire. These studies have shown that the dynamic displacements of the combined system are determined primarily by the overhead line parameters rather than by the pantograph. At higher speeds droppers in the vicinity of the pantograph slacken and this is seen to influence significantly the contact force profile. On a “constant height” overhead line, the proposed “frame compensated” and “panhead inertia compensated” pantographs do not show any marked improvement in the quality of current collection.
Solution and Parameter Estimation in Linear Time-Invariant Delayed Systems Using Laguerre Polynomial Expansion
Authors: Kung Fan-Chu , Lee Hua
Published: July 2009

Finite dimensional Laguerre polynomial expansion can be applied to approximate the solution of linear time-invariant systems. Here, we extend this approach to systems with small time delay by introducing a delay matrix operator to the system equations. In addition, parameters of linear unity-feedback systems with small time delay can also be estimated by using the Laguerre expansion. In this paper we provide algorithms for large scale systems to avoid direct matrix inversion and give examples to demonstrate the approximation.
Generalized Equations of Motion for the Dynamic Analysis of Elastic Mechanism Systems
Authors: Turcic D. A. , Midha Ashok
Published: July 2009

Until recently, vibration effects have generally been neglected in the design of high-speed machines and mechanisms. This has been primarily due to the complexity of the mathematical analysis of mechanisms with elastic links. With the advent of high-speed computers and structural dynamics techniques, such as finite element analysis, this is no longer regarded as such a formidable task. To date, with few exceptions, the analysis of elastic mechanism systems have been limited to a single type of mechanism (i.e., a four-bar or slider-crank) modeled with a small number of simple finite elements (usually beam elements). This paper develops the generalized equations of motion for elastic mechanism systems by utilizing finite element theory. The derivation and final form of the equations of motion provide the capability to model a general two- or three-dimensional complex elastic mechanism, to include the nonlinear rigid-body and elastic motion coupling terms in a general representation, and to allow any finite element type to be utilized in the model. A discussion of a solution method, applications, as well as an experimental investigation of an elastic four-bar mechanism will be presented in subsequent publications.
Dynamic Analysis of Elastic Mechanism Systems. Part I: Applications
Authors: Turcic D. A. , Midha Ashok
Published: July 2009

In a previously reported work, generalized equations of motion were developed for the dynamic analysis of elastic mechanism systems. Emphasis was placed on the need for including vibration effects; these, until recently, had generally been neglected, primarily for reason of the complexity of the mathematical analysis of such systems. Finite element theory was used to facilitate the modeling of elastic mechanisms. In this work, Part I of two companion papers, an approach to the solution of the equations of motion is offered. Some related considerations are also discussed. Applications to the analysis and solution method are presented. To demonstrate generality, an example is selected wherein the geometrically complex follower link of a four-bar mechanism is modeled with quadrilateral finite elements. Part II of this paper presents an experimental investigation of an elastic four-bar mechanism.
Dynamic Analysis of Elastic Mechanism Systems. Part II: Experimental Results
Authors: Turcic D. A. , Midha Ashok , Bosnik J. R.
Published: July 2009

In an earlier publication, generalized equations of motion were presented for the dynamic analysis of elastic mechanism systems. In a subsequent work, Part I of this paper, an approach to the solution of the equations of motion and applications were presented. This paper, Part II of two companion papers, presents an experimental investigation of an elastic four-bar mechanism. The experimental four-bar mechanism coupler and follower strains help to verify those determined analytically. The strains are shown to compare very well in both amplitude as well as frequency content.
Guaranteed Tracking Behavior in the Sense of Input-Output Spheres for Systems With Uncertain Parameters
Authors: Jayasuriya S. , Rabins M. J. , Barnard R. D.
Published: July 2009

A class of dynamical systems containing uncertain elements and subject to uncertain inputs is considered. The plant parameter uncertainties are assumed to be “unknown-but-bounded.” Design criteria are given for the synthesis of controllers for such systems, which guarantee that every input within a certain neighborhood of a nominal input gives rise to a corresponding output or system response in a prespecified neighborhood of a nominal output. These tracking specifications are formulated in terms of topological neighborhoods in normed function spaces, and feedback controllers are constructed by nonlinear state observers related to the uncertain plants and utilizing the measured output. These results, based primarily on fixed-point and operator norm techniques, provide quantitative servo designs and precise error bounds for the specified tracking behavior. The applicability of such derived criteria are demonstrated through synthesized controllers for two examples: a vibration isolation problem and a speed controller.
Electro-Hydraulic Digital Control of Cone-Roller Toroidal Traction Drive Automatic Power Transmission
Authors: Tanaka H. , Ishihara T.
Published: July 2009

Continuously variable automatic transmissions can bring improved fuel economy benefits under good speed ratio changes for automobile propulsion systems in which engines can produce their power under optimum conditions. These systems require computer control for the calculation of optimum speed ratio. The paper presents design features of the electrohydraulic interface between micro-computer and cone-roller toroidal traction drive CVT, dynamic characteristics of cone roller motion, and test results of the practical computer control of CVT.
Wheel-Rail Contact Wear, Work, and Lateral Force for Zero Angle of Attack—A Laboratory Study
Authors: Kumar Sudhir , Rao D. L. Prasanna
Published: July 2009

Most of the wear indices, used in the railroad industry for predicting wheel/rail wear, are functions of angle of attack between wheel and rail. Further, the wear problem has been studied in terms of wear coefficients which relate the wear volume to the work done in the wear process. The wear-work principle, as applicable to wear indices and coefficients, is enunciated and its implications are discussed. An analysis of the wheel/rail interaction as a two point contact problem is presented. To establish the validity of the theory and applicability of the indices, results from a series of four experiments on a quarter scale laboratory rig are reported. The experiments are with “zero angle of attack” and an externally applied lateral load on the wheel, representing the idealized operation of a perfect radial truck. It is observed that contrary to the prediction, based on most of the suggested indices, there is noticeable wear of both wheel and rail even under zero angle of attack. It is concluded that lateral forces should be explicitly included in wear index formulation. Calculated values of wear coefficients, in the range 7.7E-5 to 38.0E-5 for the case of total contact slip and 21.6E-5 to 120.8E-5 for the case of adhesive or micro slip, indicate the effect of plastic flow in the contact when the Holm-Archard relation is assumed valid. Approximate validity of the Derby wear index, based on energy considerations, indicates that indices which are primarily functions of angle of attach are not quite valid for predicting field wheel/rail wear. It is also concluded that the wear-work principle as formulated in the paper can be considered to be reasonably valid.
A Simplified Modeling and Computational Scheme for Manipulator Dynamics
Authors: Horak D. T.
Published: July 2009

The complex dynamics of manipulators make design of dynamic control laws for them very difficult. Today’s industrial robots employ dynamic control laws which neglect the complex dynamics, thus leading to less than optimal response. The computational bottleneck of many advanced control schemes is an algorithm for computation of the actuator torques (forces) required to produce desired joint accelerations, for a given set of joint velocities and angles (displacements). The algorithm must be evaluated by the control computer about 100 times per second for the scheme to be effective. The previously known algorithms require large minicomputers to satisfy this speed requirement. The scheme described here, when implemented on a single processor, is about five times faster than the recursive Newton-Euler algorithm. When implemented on two processors, it is about ten times faster. The computational efficiency is achieved by partitioning the manipulator into two parts for modeling purposes. The modeling technique uses no approximations and can be applied to manipulators with up to seven links, which includes most designs presently in use.
Computer Simulation of Stick-Slip Friction in Mechanical Dynamic Systems
Authors: Karnopp Dean
Published: July 2009

Stick-slip friction is present to some degree in almost all actuators and mechanisms and is often responsible for performance limitations. Simulation of stick-slip friction is difficult because of strongly nonlinear behavior in the vicinity of zero velocity. A straightforward method for representing and simulating friction effects is presented. True zero velocity sticking is represented without equation reformulation or the introduction of numerical stiffness problems.
Displacement Control of Flexible Structures Using Electrohydraulic Servo-Actuators
Authors: McClamroch N. H.
Published: July 2009

A general approach to the displacement or position control of a nonlinear flexible structure using electrohydraulic servo actuators is developed. Our approach makes use of linear feedback of measured structural displacements plus linear feedback of the actuator control forces; a nonlinear feedforward function of the displacement command is also used for control. Based on a mathematical model of the closed loop, general conditions for closed loop stability are obtained. In the special case that the feedback is decentralized the stabilization conditions are stated in terms of simple inequalities; moreover, the stabilization conditions are robust to structural uncertainties since the conditions do not depend on explicit properties of the structure. Such robustness is a direct consequence of use of force feedback rather than, for example, acceleration feedback. Conditions are also developed for selection of the feedforward control to achieve zero steady state error; but this condition does depend on explicit properties of the structure. The theoretical results developed in the paper should provide a framework for advanced applications of control of mechanical systems using electrohydraulic servo-actuators.
A Pitch Control System for the KaMeWa Wind Turbine
Authors: Liebst B. S.
Published: July 2009

This study is the design of a pitching blade control system for the National Swedish Board for Energy Source Development KaMeWa wind turbine. Full state controllers are designed utilizing optimal control theory to reduce blade and tower vibration, power oscillations, and improve gust response. The results show that substantial vibration reduction can be obtained with the existing pitch actuators installed presently on the machine.
Impedance Control: An Approach to Manipulation: Part II—Implementation
Authors: Hogan Neville
Published: July 2009

This three-part paper presents an approach to the control of dynamic interaction between a manipulator and its environment. Part I presented the theoretical reasoning behind impedance control. In Part II the implementation of impedance control is considered. A feedback control algorithm for imposing a desired cartesian impedance on the end-point of a nonlinear manipulator is presented. This algorithm completely eliminates the need to solve the “inverse kinematics problem” in robot motion control. The modulation of end-point impedance without using feedback control is also considered, and it is shown that apparently “redundant” actuators and degrees of freedom such as exist in the primate musculoskeletal system may be used to modulate end-point impedance and may play an essential functional role in the control of dynamic interaction.
Swing-Free Transport of Suspended Objects With a Path-Controlled Robot Manipulator
Authors: Starr G. P.
Published: July 2009

Objects which cannot be directly grasped by the end effector of a robot manipulator and must be carried by a hook or similar device are susceptible to swinging during transport. For a simply suspended object, it is possible to use a path-controlled manipulator to achieve a swing-free motion. The trajectory consists of an initial acceleration to an intermediate velocity, then a secondary acceleration to final velocity. An experimental demonstration of the method is presented.
The Dynamics of Vortex Amplifiers. Part 1: Analytical Model
Authors: Kitsios E. E. , Boucher R. F.
Published: July 2009

A semi-empirical technique for the dynamic modeling of vortex amplifiers is demonstrated with reference to one particular vortex amplifier geometry. The model parameters are determined explicitly from the amplifier static characteristics and geometry except for two which are estimated from measurements of the amplifier’s dynamic response. The two are time constants associated with the chamber time delay and the vortex rotational inertia. The model is linearized about a working point and is presented in terms of an admittance matrix. The paper is continued in Part 2 where two of the amplifier’s transfer admittances are measured experimentally and compared with the model predictions.
Experiments Using Lattice Filters to Identify the Dynamics of a Flexible Beam
Authors: Sundararajan N. , Montgomery R. C.
Published: July 2009

An approach for identifying the dynamics of large space structures is applied to a free-free beam. In this approach the system’s order is determined on-line, along with mode shapes, using recursive lattice filters which provide a linear least square estimate of the measurement data. The mode shapes determined are orthonormal in the space of the measurements and, hence, are not the natural modes of the structure. To determine the natural modes of the structure, a method based on the fast Fourier transform is used on the outputs of the lattice filter. These natural modes are used to obtain the modal amplitude time series from the measurements. The modal time series provides the input data for an output error parameter identification scheme that identifies the autoregressive moving average (ARMA) parameters of the difference equation model of the modes. Results using this approach for experimentally identifying the dynamics of a flexible beam hardware are presented.
A Suboptimal Design Approach to the Ring Diameter Control for Ring Rolling Processes
Authors: Yun J. S. , Cho H. S.
Published: July 2009

Although the ring rolling process is now finding increasing applications in many wider fields, analytical design methodology for controlling the process has been little explored. This paper considers an analytical design approach to the problem of controlling the pressure roll motion which critically affects the quality of rolled products. For this purpose a suboptimal PID controller was designed based upon the nonlinear rolling process model, in order to control the pressure roll movement to track a desired ring diameter growth profile as close by as possible during the rolling cycle. A series of simulations was performed to demonstrate the effectiveness of this controller. The results show that the proposed suboptimal controller can produce rolled rings of closer dimensional tolerances as well as improve the tracking performance, as compared with nonoptimal controllers.
The Open and Blocked Distributed Air Transmission Lines by the Fast Fourier Transform Method
Authors: Tsang S. H. L. , Benson M. W. , Granberg R. H.
Published: July 2009

This paper deals with the digital computer simulation of a distributed air transmission line subjected to an impulse, step, or arbitrary excitation. The rationale is based on the inverse Fourier transform principle: R(t)=F−1{G(jω)•P1(jω)} where R(t) is the response, G(jω), the system frequency function, and P1(jω), the frequency spectrum of the input function. For input flow prediction, G(jω) is the input admittance. G(jω) represents the transfer function for pressure calculation. The predicted dynamics of a blocked and an open line subjected to arbitrary periodic excitation are compared with experimental measurements. The paper also presents the mathematical proofs to illustrate the functional behaviors of G(jω) as ω is varied from −∞ to −∞.
Torque on the Swashplate of an Axial Piston Pump
Authors: Zeiger G. , Akers A.
Published: July 2009

As part of a study involving methods of control of an axial piston pump, it is required to obtain linear or linearized equations of motion of the system’s states. The torque imposed on the plate by the pumping action of the pistons is the most important term in the equation of motion of the swashplate. The torque is a result of a nonlinear and partly discontinuous relationship; this relationship being a function of the geometrical features of the pump and the system operating conditions. Mathematical equations describing swashplate torque are derived from general hydraulic and mechanical considerations given in this paper. This mathematical model can be linearized so that linear parameters for the equation of motion of the swashplate can be obtained. In addition, results of predictions made by the model are presented and compared with some experimental data provided by Sundstrand. An indication is also given as to changes in torque resulting from variation in swashplate angular velocity and timing position of the valve plate.
The Effect of Oil Entrapment in an Axial Piston Pump
Authors: Lin S. J. , Akers A. , Zeiger G.
Published: July 2009

Values of pressure caused by entrapment beneath a valve plate have been calculated. The technique used consists of the solution of the dynamical equation of motion in the piston control volume. Instantaneous and average values of torque have also been deduced from the pressure distribution. Plots have been constructed showing the effect of swashplate angle, pump angular rotation, discharge pressure, and entrapment angle upon instantaneous pressure, torque, and average torque for a typical axial piston pump.
Dynamic Modeling and Simulation of Gaseous Systems
Authors: Wu S. Z. , Wormley D. N. , Rowell D. , Paynter H. M.
Published: July 2009

A general computer-based mathematical modeling system for analyzing air/gas system dynamics has been developed. A set of generic lumped and distributed elements are interconnected by generalized junction structures to represent system configurations. The dynamic response of pressure, flow, temperature, and heat transfer rate at any point in a system, due to control actions, or fluid, thermal, or mechanical disturbances can be determined. The model has been used to analyze furnace implosion and disturbance propagation problems in fossil fuel power plants. To illustrate the modeling techniques, a model of a coal-fired plant has been constructed and pressure transients computed following a fuel trip. The model simulation predictions of the furnace pressure excursions are in close agreement with the data from field tests.
An Innovation-Based Methodology for HVAC System Fault Detection
Authors: Usoro P. B. , Schick I. C. , Negahdaripour S.
Published: July 2009

Although Energy Management and Control Systems (EMCS) have since the early 1970’s contributed significantly to the reduction (20-40 percent) of energy use in buildings without sacrificing occupants’ comfort, their full capabilities have not been completely realized. This is in part due to their inability to quickly detect and compensate for failures in the Heating, Ventilation and Air Conditioning (HVAC) system. In fact, no matter how good the control scheme for the HVAC system might be, the presence of undetected faults can completely offset any expected savings. This paper presents a methodology for detecting faults in an HVAC system using a nonlinear mathematical model and an extended Kalman filter. The technique was implemented in a computer program and successfully used to detect “planted” faults in simulations of the air handler unit of an HVAC system. Test results are presented to demonstrate the effectiveness of the methodology.
Application of a Model Reference Adaptive Algorithm to the Combustion Control of a Power Unit Boiler
Authors: Fernandez del Busto R. , Sanchez E. N. , Urbieta R. , Kaufman H.
Published: July 2009

An application of a model reference adaptive control algorithm to the combustion control of a 300 MW power unit boiler is presented. The primary process variable to control under this scheme is the main steam pressure. The objective of this implementation is the reduction of steam pressure sensitivity to load variation. A comparison between the plant behavior with classical PID combustion control and the adaptive algorithm shows than the latter scheme produces a smoother response.
Robust Trajectory Following Control of Robotic Systems
Authors: Singh S. N. , Schy A. A.
Published: July 2009

Using an inversion approach we derive a control law for trajectory following of robotic systems. A servocompensator is used around the inner decoupled loop for robustness to uncertainty in the system. These results are applied to trajectory control of a three-degrees-of-freedom robot arm and control laws Cθ and CH for joint angle and position trajectory following, respectively, are derived. Digital simulation results are presented to show the rapid trajectory following capability of the controller in spite of payload uncertainty.
Self-Tuning Manipulator Control in Cartesian Base Coordinate System
Authors: Koivo A. J.
Published: July 2009

A discrete-time stochastic model for the motion of a robotic manipulator system is introduced. The input vector consists of the voltages to the joint motors, and the output vector has the velocities (positions) of the gripper expressed in the world (xyz) coordinate system as the components. The model is a linear multivariate autoregressive model with external input. The unknown parameters of the model can be calculated recursively on-line by the least squares algorithm. An adaptive self-tuning type controller is then designed by minimizing the expected value of a quadratic criterion. This performance index penalizes the deviations of the actual path of the gripper from the desired values expressed in the Cartesian coordinate system and the use of the energy associated with the input vector. Digital simulation results using the parameter estimation and the control algorithms are presented, and discussed.
A Direct Digital Control Algorithm for Control of a Single Environmental Space
Authors: Cherchas D. B. , Abdelmessih A. , Townsend M.
Published: July 2009

A direct digital control algorithm for control of dry bulb temperature in a single environmental space is developed. The algorithm is based on a bilinear mathematical model, developed in the paper, of the response of the space dry bulb temperature and moisture content. The algorithm is somewhat unique in that it includes feedback and feedforward terms in a manner respecting the bilinear nature of the controlled process and as well, minimizes a practical performance index. The discrete time form of the algorithm is presented and simulation results given.
Heat Transfer Effects on the Frequency Response of a Pneumatic Nozzle Flapper
Authors: Kagawa Toshiharu
Published: July 2009

The dynamics of a pneumatic nozzle flapper are influenced by the heat transfer characteristics in the air chamber. In this paper the transfer function for a nozzle flapper is analytically derived considering the heat transfer. As a result it is shown that the system can be expressed as a second order time lag system. In the experiments, the frequency response tests have been conducted for different heat transfer conditions, and the heat transfer effect is clearly shown. The experimental data are in satisfactory agreement with the calculated frequency responses.
Real Time Vibration Control of Rotating Circular Plates by Temperature Control and System Identification
Authors: Mote C. D. , Rahimi A.
Published: July 2009

A system for real-time control of the transverse vibration of a rotating circular plate, based on a thermal stressing technique and dynamic system identification, is presented in this paper. In this method the natural frequency spectrum of the plate is modified through the purposeful introduction of thermal membrane stresses. Evaluations with comptuer simulations and experimental measurements on a thin circular plate verify the system capability to suppress transverse vibration in a changing thermal environment.
Vortex Flow Controllers in Sanitary Engineering
Authors: Brombach H.
Published: July 2009

Flow control problems in combined sewerage systems can be solved with the aid of a new variation of the vortex amplifier. This valve has no moving parts, and comes under the category of pure fluidics; it has a conical vortex chamber and a single inlet port. Depending on the level of water in the vortex chamber the flow pattern may be either axially symmetrical or axially asymmetrical. This effect enables the device to alter its flow resistance in response to the input pressure. Several hundred of this type of the flow controller are already in operation. An example of their application is described below.
A Dynamic-Test Procedure for Improving Seismic Qualification Guidelines
Authors: deSilva C. W.
Published: July 2009

Several shortcomings of available standards, regulatory guides, and review plans for seismic qualification testing are identified. A rational test nomenclature is proposed. A standard test is developed by optimizing an appropriate test severity measure function. The standard test is a rectilinear test that is equivalent to the three-degree-of-freedom test with uncorrelated excitations, recommended in IEEE-Std. 344. In terms of eigenvectors of a resulting test matrix, a dynamic interpretation is given for principal axes of a test object. The proposed approach to dynamic testing has two main advantages in comparison to the conventional approach of black-box testing. Firstly, knowledge pertaining to test-object dynamics is directly employed in its development. Secondly available information on possible modes of failure in the overall system can be conveniently incorporated into the formulation.
A Calibration and Estimation Filter for Multiply Redundant Measurement Systems
Authors: Ray Asok , Desai Mukund
Published: July 2009

An adaptive filter has been developed for calibration and estimation in multiply redundant measurement systems. The filter is structured in the framework of a fault detection and isolation (FDI) methodology where the decisions are made on the basis of consistencies among all redundant measurements. The consistent measurements are calibrated on-line to compensate for their errors. An estimate of the measured variable is obtained as a weighted average of the calibrated measurements where the individual weights are adaptively updated on-line on the basis of the respective a posteriori probabilities of failure instead of being a priori fixed. The calibration and estimation algorithm is suitable for real-time applications using commercially available microcomputer systems, and has been verified by on-line demonstrations in an operating nuclear reactor.
Optimal Deterministic State Estimation—A First Step
Authors: Jacquot R. G.
Published: July 2009

Optimal deterministic observers are derived for all first order linear time invariant systems. The optimization process consists of minimizing an objective function which is quadratic in the observer gain and in the estimation error. The objective function was chosen such that the resulting observer gains would be independent of system initial-condition which would, in general, be unknown to the state estimator. The results of this optimization are sensible in the light of the stochastic estimation results of Kalman.
Control of Systems Subject to Small Measurement Disturbances
Authors: Sworder D. D.
Published: July 2009

When a controlled system is subject to external disturbances of large magnitude, the regulator often uses a mixed strategy, combining a feedforward link to neutralize the primary impact of the disturbance, and a feedback link to reduce the effect of any residual. If there is a possibility of error in measuring the disturbance, the problem becomes more complex. A sophisticated regulator might even try to “learn” the true value of the disturbance. Attempts to design such an intelligent regulator usually lead to intractable synthesis equations. This paper provides a simple alternative for the case in which the measurement of the disturbance is close to the true value. A study of a simple model of a solar-powered boiler shows that the performance of the proposed regulator is near that attainable by much more complicated controllers.
Limit Cycle Prediction Conditions for a Class of Hydraulic Control System
Authors: Cox C. S. , French I. G.
Published: July 2009

This paper presents the conditions necessary to sustain a limit cycle in hydraulic position control systems with displacement feedback. The limit cycle performance of the system is then examined when the temperature of the working fluid varies between 283K(10°C) to 343K(70°C). Results are presented for an electrohydraulic system driving a load comprising inertia, viscous friction, and coulomb friction.
Automatic Computation of the Screw Parameters of Rigid-Body Motions. Part I: Finitely-Separated Positions
Authors: Angeles Jorge
Published: July 2009

Introduced in this paper is a novel approach that leads to efficient algorithms for computing the screw parameters of rigid-body motions. This is based on invariants associated with the said motions. Finitely-separated positions are treated in this paper, infinitesimally-separated positions being the subject of an accompanying paper. The algorithms presented in both papers are meant for the real-time computation of the aforementioned parameters.
Automatic Computation of the Screw Parameters of Rigid-Body Motions. Part II: Infinitesimally-Separated Positions
Authors: Angeles Jorge
Published: July 2009

This paper follows a previous one on the computation of the screw parameters of rigid-body motions defined by two finitely-separated positions. The subject of the present paper is the computation of the said parameters associated with motions defined by two infinitesimally-separated positions. Both papers are based on invariant concepts, associated with the motion under study, which lead naturally to efficient real-time implementable algorithms.
A Practical Approach to Nonlinear Estimation by Using the Maximum Entropy Principle
Authors: Jumarie Guy
Published: July 2009

The problem of estimating the state of a continuous markovian process in the presence of nonlinear observation (nonlinear filtering) may be considered as being completely solved on a theoretical standpoint. All the difficulties arise in the practical applications which require new ways of investigation: search for special approaches related to special problems, and search for improvement of the numerical techniques which are now available. In fact, nonlinear filtering is basically an infinite dimensional problem, and any approximation should work in a finite dimensional space. The paper proposes an approach without using stochastic differential equations. The continuous markovian process is defined by its transition moments only and therefore one can derive the equation of state moments. When the transition moments are polynomials, the state moments are then given by an infinite set of linear differential equations. Likewise when the observation is polynomial, an infinite set of linear equations provides estimates of the state moments in terms of the observation moments. Given the estimates of the state moments, and using the maximum entropy principle we will obtain the corresponding probability density, and therefore the estimate of the state. When the nonlinear functions are not polynomials, it will be possible to apply the method above, using a polynomial approximation.
Vibro-Impact Analysis of Control Systems With Mechanical Clearance and Its Application to Robotic Actuators
Authors: Stepanenko Y. , Sankar T. S.
Published: July 2009

The paper presents a new approach to the analysis of the influence of breaks in the kinematic chains on the stability of robotic actuators possessing elastic properties. An appropriate dynamic model of a nonlinear element with clearance and elasticity is developed and an explicit solution is obtained for the harmonic vibro-impact motions of the model. The describing function of the nonlinear element is derived and is applied to the analysis of high frequency limit cycles in the actuators.
Stochastic Optimal Control of Vehicles With Elastic Body and Active Suspension
Authors: Hac´ Aleksander
Published: July 2009

A discrete-continuous vibrating system, which can be treated as a model of a vehicle with an active suspension moving on a randomly profiled road, is considered in this paper. By the use of stochastic optimal control and estimation theory the suspension control forces and the steady-state behavior of an optimally controlled system in the presence of measurement errors are calculated and compared with the performance of an optimal passive system. The emphasis is on modeling and measurement problems. The need for taking body elasticity into account in the vehicle model is considered and the influence of sensor arrangement and accuracy upon the performance of the active system is determined.
Control of a Dynamical Biped Locomotion System for Steady Walking
Authors: Furusho J. , Masubuchi M.
Published: July 2009

A dynamic biped locomotion robot which realizes high speed movement is presented. Its walking cycle is about 0.45 s, its speed is about 0.8m/s, and its appearance resembles a human walking. A hierarchical control structure is adopted at the lower level at which the local feedback is implemented. The reference signal to each local controller is supplied from its higher level. The stability of steady walking is examined by using the reduced order model which has been derived by the authors and it is assured by experiments.
Dynamic Simulation of a Leadscrew Driven Flexible Robot Arm and Controller
Authors: Chalhoub Nabil G. , Ulsoy A. Galip
Published: July 2009

High performance requirements in robotics have led to the consideration of structural flexibilty in robot arms. This paper employs an assumed modes method to model the flexible motion of the last link of a spherical coordinate robot arm. The model, which includes the non backdrivability of the leadscrews, is used to investigate relationships between the arm structural flexibility and a linear controller for the rigid body motion. This simple controller is used to simulate the controllers currently used in industrial robots. The simulation results illustrate the differences between leadscrew driven and unconstrained axes of the robot; they indicate the trade-off between speed and accuracy; and show potential instability mechanisms due to the interaction between the controller and the robot structural flexibility.
An Adaptive Control Scheme for Mechanical Manipulators—Compensation of Nonlinearity and Decoupling Control
Authors: Horowitz Roberto , Tomizuka Masayoshi
Published: July 2009

This paper presents a new adaptive control scheme for mechanical manipulators. Making use of the fundamental properties of the manipulator equations, an adaptive algorithm is developed for compensating a nonlinear term in the dynamic equations and for decoupling the dynamic interaction among the joints. A computer simulation study is conducted to evaluate the performance of a manipulator control system composed of the manipulator, adaptive nonlinear compensator/decoupling controller and state feedback controller with integral action. Simulation results show that the manipulator control system with adaptive controller is insensitive to variations of manipulator configurations and payload.
Joint Self-Tuning With Cartesian Setpoints
Authors: Backes P. G. , Leininger G. G. , Chung Chun-Hsien
Published: July 2009

A joint coordinate self-tuning manipulator control method is presented which uses Cartesian setpoints. The method is capable of both position and hybrid control. Position and force errors are transformed from Cartesian coordinates to position and force errors at the joints. The position and force errors at each joint are combined into one hybrid error that is eliminated using pole-placement self-tuning. Real time position and hybrid control results are given. No prior knowledge of manipulator or load dynamics is required and real time control results show that the goal of consistent control with changing load dynamics is achieved. The major cause of error in position and hybrid control is the large friction effects in the joints.
Multivariable Adaptive Model Matching Using Less A Priori Information
Authors: Das M.
Published: July 2009

The interactor matrix of a system plays an important role in the design of model-matching adaptive controllers for multivariable systems. With the purpose of reducing a priori information necessary for such a design, this note presents a reformulation of the basic design methodology of a well known multivariable, adaptive model-matching algorithm and shows how one can estimate the nondiagonal entries of the interactor matrix from a priori knowledge of the degrees of its diagonal entries alone.
Inverse Kinematic Solutions With Singularity Robustness for Robot Manipulator Control
Authors: Nakamura Yoshihiko , Hanafusa Hideo
Published: July 2009

The singularity problem is an inherent problem in controlling robot manipulators with articulated configuration. In this paper, we propose to determine the joint motion for the requested motion of the endeffector by evaluating the feasibility of the joint motion. The determined joint motion is called an inverse kinematic solution with singularity robustness, because it denotes feasible solution even at or in the neighborhood of singular points. The singularity robust inverse (SR-inverse) is introduced as an alternative to the pseudoinverse of the Jacobian matrix. The SR-inverse of the Jacobian matrix provides us with an approximating motion close to the desired Cartesian trajectory of the endeffector, even when the inverse kinematic solution by the inverse or the pseudoinverse of the Jacobian matrix is not feasible at or in the neighborhood of singular points. The properties of the SR-inverse are clarified by comparing it with the inverse and the pseudoinverse. The computational complexity of the SR-inverse is considered to discuss its implementability. Several simulation results are also shown to illustrate the singularity problem and the effectiveness of the inverse kinematic solution with singularity robustness.
Improvement in the Computing Time of Robot Manipulators Using a Multimicroprocessor
Authors: Watanabe T. , Kametani M. , Kawata K. , Tetsuya K.
Published: July 2009

A multimicroprocessor having a hardware circuit designed to aid the synchronization of CPUs and software to schedule tasks on the CPUs is proposed. The system is applied to the calculation of the joint angles of six-axis robot manipulators. It is verified that the scheduling software gives the optimum schedule for an elbow manipulator and a sub-optimum one for the Stanford manipulator. Actual calculations on the multiprocessor verifies that the computing time is decreased to 3.6 ms by the proposed parallel processing using seven CPUs and seven APUs, while it takes about 20 ms by ordinary processing using one CPU and one APU.
A Finite Element/Lagrange Approach to Modeling Lightweight Flexible Manipulators
Authors: Usoro P. B. , Nadira R. , Mahil S. S.
Published: July 2009

This paper presents a finite element/Lagrangian approach for the mathematical modeling of lightweight flexible manipulators. Each link of the manipulator is treated as an assemblage of a finite number of elements for each of which kinetic and potential energies are derived. These elemental kinetic and potential energies are then suitably combined to derive the dynamic model for the system. It is contended that satisfactory modeling and analysis of the manipulator dynamics can lead to the use of advanced control techniques to solve some of the problems associated with the flexure of otherwise attractive lightweight manipulator arms. Detailed model development and simulation results for the case of a two-link manipulator system are presented.
A Preliminary Investigation of the Dynamic Stability of Flexible Manipulators Performing Repetitive Tasks
Authors: Streit D. A. , Krousgrill C. M. , Bajaj A. K.
Published: July 2009

The governing equations of motion for the compliant coordinates describing a flexible manipulator performing repetitive tasks contain parametric excitation terms. The stability of the zero solution to these equations is investigated using Floquet theory. Analytical and numerical results are presented for a two-degree-of-freedom model of a manipulator with one prismatic joint and one revolute joint.
Adaptive Time Optimal Control for Ship Steering
Authors: Fukino Masato , Tomizuka Masayoshi
Published: July 2009

This paper proposes an adaptive time optimal control algorithm for ship steering in course changes. Dynamics of the ship are presented by a third order differential equation model. The time optimal control law is obtained by applying the Successive Order Hightening Method. It is combined with a least squares type parameter estimation algorithm to obtain the adaptive time optimal controller. The proposed control scheme is evaluated by a computer simulation study.
Two Contrasting Versions of the Optimal Active Vehicle Suspension
Authors: Karnopp Dean
Published: July 2009

It is generally agreed that vehicle suspensions should isolate the body from roadway unevenness inputs but it is less clear on which other functions are most important. Some studies focus on keeping the wheel-road contact force excursions as small as possible for safety reasons and others focus on limiting the main suspension deflection for good rigid body motion control. In this paper, two performance indices are used which lead to optimal state variable feedback laws for the suspension force. Body isolation is traded off in one case against contact force variation and in the other against suspension deflection. The use of symmetric root locus sketches shows the types of system that result in both cases. It is shown that optimal active suspensions designed according to different criteria are not necessarily comparable and it may not be fair to compare an optimal suspension with a conventional one, unless all aspects of suspension performance are considered simultaneously.
A Note on Matrix Chebyshev-Pade´ Approximations to Continuous State Modeling
Authors: Hwang Chyi , Yung Chee-Fai
Published: July 2009

In this note, a new method of using matrix Chebyshev-Pade´ approximations is presented for modeling continuous state from a discrete state equation. The method is illustrated with an example.
On Reducing the Order of Transfer Functions
Authors: Vepa Ranjan
Published: July 2009

A simple method of reducing the number of real negative poles of a transfer function is described in detail.
Multistep Self-Tuning Prediction
Authors: Espan˜a M. D.
Published: July 2009

An optimal multistep predictor based on the 1-step-ahead predictor is presented. It is shown that parallel predictors need not be implemented in order to predict the output of some stochastically disturbed system over a future horizon of sampling instants. When the parameters are not known the self-tuning property of the 1-step ahead predictor combined with a least-square recursive identification algorithm is inherited by the future predictions obtained on its bases. The structure complexity of the problem can thus be reduced to its minimal expression, i.e., the 1-step-ahead step-tuning predictor.
Evaluation of DC Servo Machine Tool Feed Drives as Force Sensors
Authors: Stein J. L. , Colvin D. , Clever G. , Wang C.-H.
Published: July 2009

Unmanned machine tools as part of an automated factory require reliable, inexpensive sensors to provide machine and process information to the controller. The electric current in the DC motor of a CNC machine tool can be inexpensively measured and used to calculate the tool/workpiece cutting force and the forces associated with drive system components. In order to characterize the bandwidth, sensitivity and accuracy of current monitoring on the feed system of a CNC lathe, a dynamic lumped parameter model of this sensor system is developed. The model is used to identify the system components that have a dominant effect on the behavior of the sensor. Tests were conducted in order to determine the model parameters, verify the model, and determine the signal-to-noise (S/N) ratio of the sensor. The bandwidth of this sensor is predicted to be 80 Hz. Tests show that the S/N ratio is low but can be improved by a trade-off with the system bandwidth. The bandwidth is limited by the characteristics of the SCR amplifier. In addition, the sensitivity and accuracy of calculating the feed force component of the cutting force from the total current used by the feed motor is limited by the pitch of the ball screw and friction coefficient variations in the slide. Feed system design changes, to improve the S/N ratio of the feed system as a tool and machine force sensor, are discussed.
Signal Shaping of Fluid Transmission Lines Using Parallel Branching
Authors: Yang W. C. , Margolis D. L.
Published: July 2009

The dynamic characteristics of fluid transmission lines with a parallel branching line are analyzed in both time and frequency domains using modal approximation techniques which enable us to use linear system theory. For hydraulic blocked lines, root loci of dominant modes as functions of parallel line length ratio, branching location and line characteristic parameters are obtained, and also unit step and frequency responses are illustrated for various parallel line configurations. By properly adding a parallel branching line, shaping of frequency response and control of fluid transients can be accomplished in various advantageous ways, i.e., shifting the resonant frequencies, improving the resonant quality, suppressing the frequency response for particular bands of frequencies including the resonance regions, phase leading. The steady state conditions are derived in an exact manner and a modal bond graph model is presented.