bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of a Pneumatically Coupled Cam-Actuated Mechanism
Authors: LeQuoc S. , Cheng R. M. H.
Published: July 2009

Cam-actuated mechanism with a pneumtic coupling is a design improvement upon the conventional system. Pneumatic dashpots are used which provide a cushioning effect, thus reducing the wear and tear of system components. This paper investigates the dynamic behavior of such a system based on a lumped parameter model with a damping factor which is a nonlinear function of the frequency. A digital computer is used as a design tool to determine the effect on the performance of changing design parameters. It is found that the system amplitude ratio peak depends largely upon the pneumatic damper orifice area and that a proper selection of the orifice area will yield a minimum resonance amplitude ratio.
A One Dimensional Crystal With Nearest Neighbors Coupled Through Their Velocities
Authors: Boyd J. N. , Raychowdhury P. N.
Published: July 2009

We consider a circular array of point masses connected by springs of non-negligible mass. In the Lagrangian for the harmonic motions of this system, the movements of neighboring point masses are coupled through both the kinetic and potential energies. By use of transformations derived from the theory of projection operators, we simplify the Lagrangian and obtain the natural frequencies of the motions of the system as functions of the number of particles present. We note that for large numbers of particles, the results for our circular array will yield the frequencies of a one dimensional crystal.
A Dynamic Model of a Concentric LADD Actuator
Authors: Pottebaum K. L. , Beaman J. J.
Published: July 2009

A LADD actuator is a device capable of converting rotational motion to translational motion and has potential for use in manipulators, robotics, and prosthetics. Two low order lumped parameter dynamic models of a concentric LADD actuator have been formulated and experimentally verified. The sixth order model includes elasticity effects while the second order model does not. Both of these models are presented in bond graph terminology in order to ease their use in overall system models.
Asymptotic Behavior of the Closed Loop Poles of Linear Optimal Multivariable Systems
Authors: Johnson M. A. , Grimble M. J.
Published: July 2009

A new theory to describe the asymptotic optimal closed-loop pole positions and their related eigenvectors is presented. This is accomplished by utilizing the optimal return difference relation in a matrix/input vector description of the asymptotic eigenstructure. The paper contains an analysis for the finite closed-loop positions showing that for nonsquare systems, there can be finite closed loop-poles not associated with the system invariant zeros. Also presented is an elementary analysis for the asymptotically infinite closed-loop pole positions. Introduced here are the concepts of Butterworth patterns and some simple subspace characterisations of the input vector directions.
Weld Pool Impedance Identification for Size Measurement and Control
Authors: Zacksenhouse M. , Hardt D. E.
Published: July 2009

A primary indicator of weld quality is the size of the bead produced, and for full penetration welds this size parameter can be reduced to the width of the backbead. A method for determining this width in real-time is proposed that measures the natural frequency of pool motion when driven by a time varying arc plasma force. This method is developed analytically and verified experimentally for stationary weld pools. A control system based on this measurement scheme is also developed and simulation results are presented.
A Fluidic Regenerative Filtration System for Hot Gas Cleaning
Authors: Owen Ieuan , Syred Nick , Reed G. P.
Published: July 2009

Combined power cycles are being developed in which low calorific value fuel gas is produced by a fluidised bed coal gasifier at high temperatures and pressures (up to 1000°C and 20 bar) to be burned and expanded through a gas turbine. The turbine specifications required the removal of all particulate material greater than 5 μm. To ensure adequate collection efficiencies it may be necessary to use filtering media such as granular beds or ceramic fibres. Filters, however, need to be replaced or regenerated at regular intervals in order to maintain the pressure differentials across them to within specified levels. This paper describes how fluidic valves (vortex amplifiers) can be used in the hostile conditions to provide the switching capability in a regenerative filtration system. A penalty is incurred in using the valves in that they require an extraneous control fluid to perform the switching function. Results of experiments at elevated temperatures together with an analysis of the system at high pressures show that in a practical system the dilution of the mainstream fuel gas by the control gas can be reduced to 0.35 percent. The fluidic switching circuit is shown to be a highly effective system for handling gas flows at elevated temperatures and pressures.
Investigation of a Technique for the Differentiation of Empirical Data
Authors: Trujillo D. M. , Busby H. R.
Published: July 2009

A dynamic programming filter is derived to estimate the first and second derivatives of empirical data. A series of numerical experiments are conducted using a known differentiable function with various amounts of added random noise.
Design of a Digital Controller Based on Series Expansions of Pulse Transfer Functions
Authors: Inooka H. , Obinata G. , Takeshima M.
Published: July 2009

By considering the rapid growth of microcomputer technology, it is now possible to implement various control algorithms into a microcomputer and to use it as a single-loop digital controller. This paper considers a design of a digital controller which achieves an arbitrarily specified closed-loop response. A linear equation is obtained for unknown parameters of such a controller based on series expansions of relevant pulse transfer functions. Some examples are given to show the characteristic features of the method.
Observer Design of Bilinear Systems
Authors: Hsu Chin Shung , Karanam V. R.
Published: July 2009

In this paper, recent results on the observer design of bilinear control systems (BLS) are first reviewed. Different design procedures are examined with respect to their associated observer error behavior. A new class of BLS observers which can be designed via pole-assignment algorithms is then presented.
Identifiability of Nonlinear Systems With Hysteretic Elements
Authors: Andronikou A. M. , Bekey G. A. , Hadaegh F. Y.
Published: July 2009

This paper is concerned with the conditions under which deterministic systems containing a hysteresis-type nonlinearity are identifiable from input-output measurements. The approach to the problem requires that identifiability conditions for appropriately defined nearly-equivalent systems be obtained initially. Then conditions under which identifiability of the nearly-equivalent nonlinear (but non-hysteretic) system imply the identifiability of the original hysteretic system are obtained. Sufficient conditions for identifiability of these systems are presented.
Time Aliasing: A Digital Data Processing Phenomenon
Authors: Thornhill R. J. , Smith C. C.
Published: July 2009

The frequency sampling theorem is developed and interpreted for a function of frequency which was sampled either directly or indirectly by spectral identification techniques. An example of the results of time aliasing when the frequency resolution is too coarse is presented. A generalized window is developed which implements a zoom inverse discrete Fourier transform for avoiding undesirable time aliasing effects.
Determination of Critical Parameters in Large Flexible Space Structures With Uncertain Modal Data
Authors: Yedavalli R. K. , Skelton R. E.
Published: July 2009

This paper addresses the problem of control design for large flexible space structures with uncertain modal data. The concepts of modal cost analysis are applied to flexible space structures with these uncertain parameters: modal damping, modal frequencies, and mode shapes at actuator (sensor) locations. A quadratic function of displacements and displacement rates is used as a performance metric. In this case it is possible to obtain explicit formulas for the cost contributions labeled “modal costs” and “parameter costs.” This type of cost decomposition analysis by which one can determine the significant modes and parameters can be useful in model reduction, parameter estimation, and structure redesign. The proposed technique is applied to the “Purdue Model,” a generic model for a two dimensional flexible structure.
Pseudo Bond Graph Representation of PWR Pressurizer Dynamics
Authors: Tylee J. L.
Published: July 2009

A fifth-order nonlinear model of a pressurized water reactor (PWR) pressurizer is developed using a pseudo bond graph approach. The model assumes separation of the vapor and liquid phases within the pressurizer and bulk condensation and boiling are included. An iterative procedure is employed to compute pressurizer pressure and water level. The model performance is validated using data obtained from a PWR test facility. In those validations, model predictions of pressure and level are (with one exception) always within actual measurement error bounds.
Effect of Tubing on Measurements of Small Transient Pressure Signals in Liquids
Authors: Farid M. M.
Published: July 2009

It is often necessary to connect the pressure transducer used for measurements of static and dynamic pressure signals to the pressure source by means of a connecting tube. The effects of the tube length and diameter on a relatively small step pressure signal in a liquid system have been studied experimentally and analyzed theoretically. Theoretical equations to predict the natural frequency and the damping coefficient of the system are obtained so that the proper length and diameter of tubing can be selected for minimum distortion of the step input signal. Agreement between theoretical predictions and experimental measurements was found to be reasonably good.
A Dynamic Model of a Molecular Sieve Bed With Nonlinear and Coupled Isotherms
Authors: Beaman J. J. , Healey A. J. , Werlin J.
Published: July 2009

A mathematical model of the O2-N2 separation process in a molecular sieve bed was developed and experimentally verified. Oxygen and nitrogen breakthrough experiments were performed on a single bed packed with molecular sieve 5A. In these experiments, the bed had initially adsorbed either pure oxygen or nitrogen and then a constant inlet flow of nitrogen or oxygen was switched on the bed. The outlet oxygen mole fraction and mass flowrate were then recorded. This was done at several pressures and flowrates. The model predictions agreed with the experimental data when a linear oxygen isotherm and a nonlinear Langmuir isotherm for nitrogen were used and when these were coupled. The numerical scheme presented in this study to solve the system equations makes efficient use of computation time.
Surface Roughness Measurement With Fiber-Optics
Authors: North W. P. T. , Agarwal A. K.
Published: July 2009

This paper describes an experimental investigation of a technique for the measurement of surface roughness of “ground” surfaces using fiber-optics. A pair of fiber-optic bundles of similar specifications are used to carry both the incident light to and the reflected from the object surface at different angles of incidence. It has been shown that the ratio of reflected intensities is found to vary inversely as the cube of the average surface roughness.
Static Shape Determination and Control of Large Space Structures: II. A Large Space Antenna
Authors: Weeks Connie J.
Published: July 2009

An integral operator approach is used to derive solutions to static shape determination and control problems associated with large space structures. Problem assumptions include a linear self-adjoint system model, observations and control forces at discrete points, and quadratic performance criteria for the comparison of estimates or control forces. Solutions reduce to the solution of linear equations of dimension on the order of the numbers of observations or control forces. Results are illustrated by simulations with a finite element model of a large space antenna. Modal expansions for terms in the solution algorithms are presented, using modes from the static or associated dynamic model. These expansions provide approximate solutions in the event that a closed form analytical solution to the system boundary value problem is not available.
Identification of Linear Structures
Authors: Wolf B.
Published: July 2009

Experimental frequency response data for a linear dynamic system is used to obtain system transfer functions. An easily implemented multi-degree-of-freedom technique which is applicable to linear structures having moderate, non-proportional viscous damping is presented. It is shown that experimental data at the resonant and antiresonant frequencies, together with high and low frequency data, are sufficient to identify the system.
Optimal Cable Configurations for Passive Dynamic Control of Compliant Towers
Authors: Wilson J. F. , Orgill G.
Published: July 2009

Whether in storm or normal seas, the ideal offshore cable-stayed compliant tower moves in harmony with the wind and waves. A properly tuned cable configuration is the key to controlled dynamic response. Formulated here are a nonlinear dynamic model involving wind, wave, current, tower, and cable interactions and a cable optimization algorithm. The objective function, the rms tower rotation, is minimized subject to appropriate constraints involving compatible system geometries and loads, as well as bounds on the platform level accelerations needed for human comfort. Tower motion is limited to a plane.
On Generalized Hopf Bifurcations
Authors: Huseyin K. , Atadan A. S.
Published: July 2009

Two distinct degenerate Hopf bifurcation phenomena associated with autonomous lumped-parameter systems are explored in great detail via the intrinsic harmonic balancing method. It is assumed that the Hopf’s transversality condition is violated and certain other conditions prevail. In one of the cases, the system exhibits a cusp shape bifurcation path which exists for either positive or negative values of the system parameter. On the other hand, the second case is concerned with a tangential bifurcation phenomenon which may not be exhibited unless an additional condition is satisfied. This existence condition is obtained in the course of analysis. The distinctive feature of the paper is that the results concerning the bifurcating paths and limit cycles are given in general, explicit forms which are expected to be very useful in a variety of applications.
Minimization of the Variance in Oil-Film Damping Coefficient Estimates
Authors: Sahinkaya M. N. , Turkay O. S. , Burrows C. R.
Published: July 2009

The frequency-domain algorithm developed by the authors to estimate oil-film bearing coefficients uses a Least Squares estimator and produces the variances and confidence bounds for the estimates. The variances can be minimized by correct design of the experimental procedure as well as by the data analysis package. The coefficient estimates are obtained by applying a multi-frequency test signal, measuring the applied force and corresponding journal displacements along orthogonal axes, and implementing the estimator. The paper discusses the use of D-optimality to select the measurement axes to improve the quality of the estimates. Experimental results obtained from a squeeze-film bearing rig are presented and discussed.
Impedance Control: An Approach to Manipulation: Part III—Applications
Authors: Hogan Neville
Published: July 2009

This three-part paper presents a unified approach to the control of a manipulator applicable to free motions, kinematically constrained motions, and dynamic interaction between the manipulator and its environment. In Part I the approach was developed from a consideration of the fundamental mechanics of manipulation. Part II presented techniques for implementing a desired manipulator impedance. In Part III a technique for choosing the impedance appropriate to a given application using optimization theory is presented. Based on a simplified analysis it is shown that if the task objective is to tradeoff interface forces and motion errors, the manipulator impedance should be proportional to the environmental admittance. An application of impedance control to unconstrained motion is presented. The superposition properties of nonlinear impedances are used to develop a real-time feedback control algorithm which permits a manipulator to avoid unpredictably moving objects without explicit path planning.
A Real-Time Calibrated Thermal Model for Closed-Loop Weld Bead Geometry Control
Authors: Bates B. E. , Hardt D. E.
Published: July 2009

A distributed source conduction model is presented as a means for prediction and control of weld width and depth. Model inputs of arc efficiency and distribution are continuously calibrated by on-line comparison of predicted topside temperatures to measured profiles, giving low errors in weld size prediction. The technique is intended for closed-loop control of MIG and TIG partial penetration welds from topside measurements.
A Model of Full Penetration Arc-Welding for Control System Design
Authors: Hardt D. E. , Garlow D. A. , Weinert J. B.
Published: July 2009

A model of the dynamics of full penetration welding is presented that relates the heat input to the resulting width of the backbead. It is developed from a heat balance using the pool as a control volume, and is applicable primarily to autogenous gas-tungsten arc welding (GTAW). Two means of modulating the input are considered: 1) varying the torch current and 2) varying the torch travel velocity. The proposed model in both cases is first order, but it has non-constant) parameters (i.e., gain and time constant). Regardless of which input is used, the gain and time constant of the system are shown to depend strongly upon the thickness of the material, the preheat temperature, and the nominal torch velocity. These trends were confirmed in a series of open-loop step tests, where gain and time constant were directly measured, and in closed-lop tests, where step and frequency response methods were used. The resulting model permits rational high performance controller design, and the variable parameters of the system suggest the need for parameter adaptive control.
Dynamic Models for Control System Design of Integrated Robot and Drive Systems
Authors: Good M. C. , Sweet L. M. , Strobel K. L.
Published: July 2009

The design of high performance motion controls for industrial robots is based on accurate models for the robot arm and drive systems. This paper presents analytical models and experimental data to show that interactions between electromechanical drives coupled with compliant linkages to arm link drive points are of fundamental importance to robot control system design. Flexibility in harmonic drives produces resonances in the 5 Hz to 8 Hz range. Flexibility in the robot linkages and joints connecting essentially rigid arm members produces higher frequency modes at 14 Hz and 40 Hz. The nonlinear characteristics of the drive system are modeled, and compared to experimental data. The models presented have been validated over the frequency range 0 to 50 Hz. The paper concludes with a brief discussion of the influence of model characteristics on motion control design.
Pneumatic Actuators for Vehicle Active Suspension Applications
Authors: Cho D. , Hedrick J. K.
Published: July 2009

The use of actively controlled pneumatic actuators in parallel with conventional passive suspensions to improve vehicle dynamics was investigated. For application on the secondary lateral suspension of AMTRACK passenger cars, it is shown that using 4 in. (10.16 cm) bore pneumatic cylinders with a valve which has a peak flow capability of 40 SCFM (1130 1/min) at 130 psi (896 KPa) can reduce the rms carbody lateral acceleration by 46 percent and the rms secondary lateral suspension stroke by 34 percent with a power requirement of 7.6 hp (5.7 kw) per car.
An Active Suspension for a Formula One Grand Prix Racing Car
Authors: Dominy J. , Bulman D. N.
Published: July 2009

During 1982, Formula 1 racing cars generated very high downforces by the use of “ground effect” aerodynamics. Such cars required very stiff suspensions to maintain a reasonably constant ride height with the result that the slightest bump unsettled the chassis and reduced cornering speeds. A semi-active suspension would have been capable of withstanding the variations in downforce while remaining “soft” to rapid road inputs. This paper proposes such a system and decribes an analysis of its dynamic responses. It demonstates that it is able to maintain a sensibly constant ride height and attitude during cornering, braking, and acceleration, while minimizing the chassis response to individual bumps.
The Application of Shifted Legendre Polynomials to Time-Delay Systems and Parameter Identification
Authors: Chang Rong-Yeu , Wang Maw-Ling
Published: July 2009

A linear time-delay state equation is solved by the proposed shifted Legendre polynomials method. The parameter identification of such a system with time delay is also studied. The system is partitioned into several time intervals. Within a certain time interval, the state and control functions are assumed to be expressed by the shifted Legendre polynomials series. Time-delay differential equations are transformed into a series of algebraic equations of expansion coefficients. An effective algorithm is proposed to solve the time-delay system problem and to estimate the system parameters. Only a small number of leading terms of expansion coefficients is enough to get accurate results. By using such an effective computational algorithm, the calculation procedures are greatly simplified. Thus much computer time is saved.
Elimination of Drift and Asymmetry Effects in Fluidic Sensors by Feedback
Authors: Phillippi R. M. , Drzewiecki T. M.
Published: July 2009

This paper presents a feedback approach to the design of fluidic sensor circuits that will minimize drift and other unwanted offset effects, that are due to component asymmetries, and at the same time will improve the overall sensor frequency response. In this approach sensor supply pressure is generated by one output of a high gain differential regulator amplifier rather than by the raw system supply pressure. As a result, variations in system pressure, that normally would appear as sensor output drift (time varying null offset), are decoupled from the sensor. The amount of effort required to keep the sensor nulled becomes the sensor system output. When this feedback is implemented the overall dynamic response can be improved by a reduction in the fundamental circuit time constant, that is governed by the sensor dynamics, by introducing phase lead and so reducing the low frequency phase shift. Since the error signal driving the high gain regulator is proportional to the degree of sensor asymmetry, output performance of the feedback system is actually enhanced by having significant null offset characteristics. The offsets generally found in photochemically etched amplifiers and laminar jet angular rate sensors are shown to be reduced by two orders of magnitude and frequency response improved by as much as a factor of five. This technique has been applied to rate sensors, resistance bridges, pressure regulators, and airspeed sensors.
An Algorithm for Computing Nonflow Gas Processes in Gas Springs and Hydropneumatic Accumulators
Authors: Otis D. R. , Pourmovahed A.
Published: July 2009

An algorithm for computing nonflow gas processes is based on the Benedict-Webb-Rubin equation of state and a thermal time constant to describe heat transport. Specific results are presented for an accumulator charged with nitrogen operating in the range 60 to 150 atmospheres and 200 to 330°K. The computer results compare favorably with NBS nitrogen property data and with experimental measurements for an expansion process and a sinusoidal cycle.
The Dynamics of Vortex Amplifiers. Part 2: Dynamic Measurements and Comparison With Model Predictions
Authors: Boucher R. F. , Kitsios E. E.
Published: July 2009

A general experimental procedure is described for determining the linearized transfer admittances of a vortex amplifier. Flow response at the ports to a measured pressure perturbation applied to any one of them was obtained by hot wire anemometer. Self and transfer admittances were determined using a dual channel spectrum analyzer. The difficulties involved in such experiments are discussed. Measurements at two working points compare well with those predicted by the theoretical model developed in Part 1 of this paper.
Surface Profilometry Based on Fringing Capacitance Measurement
Authors: Garbini J. L. , Albrecht L. J. , Jorgensen J. E. , Mauer G. F.
Published: July 2009

A rugged, compact sensor for in-process measurement of surface finish profiles is proposed. The concept is based on the detection of variations in the fringe electric field generated between the surface and a perpendicular, ceramic-encased electrode. An analysis of both static and spatial dynamic characteristics of this “capacitive profilometer” is presented. For some surfaces, the device acts as a low-pass spatial filter, attenuating the higher spatial frequencies. A method of dynamic compensation, based on Fourier transform techniques, is developed. Experimental results demonstrate the validity of the analysis and dynamic compensation. Direct comparisons of surface profiles measured with the capacitive and standard stylus-type are presented and show good agreement.
Application of Bond Graphs to Thermofluid Processes and Systems
Authors: Shoureshi R. , McLaughlin K.
Published: July 2009

Over the past few years a study was focused on the development of bond graphs for thermofluid processes and systems using the true power variables of temperature and time rate of change of entropy. This paper summarizes results of the study. Discussion begins with the study of a simple case of single phase incompressible fluid flow and ends with a completely general case of multiphase, variable density flow. Variations in density require introduction of the momentum equation to the bond graph. Inclusion of entropy as a state variable necessitates the use of Gibb’s equation and its representation by means of bond graphs. This paper presents these formulations and representations, and compares dynamic results predicted by bond graphs with those of classical approaches.
Boiler Implosion Control in Fossil Fuel Power Plants
Authors: Wu S. Z. , Wormley D. N. , Rowell D. , Griffith P.
Published: July 2009

An evaluation of systems for control of fossil fuel power plant boiler and stack implosions has been performed using computer simulation techniques described in a companion paper. The simulations have shown that forced and induced draft fan control systems and induced draft fan bypass systems reduce the furnace pressure excursions significantly following a main fuel trip. The limitations of these systems are associated with actuator range and response time and stack pressure excursions during control actions. Preliminary study suggests that an alternative control solution may be achieved by discharging steam into the furnace after a fuel trip.
Energy Management of Chillers by Multilevel Control and Optimization
Authors: Kaya A. , Sommer A.
Published: July 2009

This paper deals with multilevel control and optimization of a chiller system. The system consists of multiple chillers, feed pumps, and cooling towers. A multilevel control structure is presented. The first level contains control loops for chilled water temperature, vane position, and condenser water temperature. Second level controls provide supervisory adjustments of set points of first level controls. Third level is optimum load allocation of chillers and pumps. A fourth level supervisory deals with the coordination of conflicting goals of subsystems to provide a load strategy. Performance analysis (monitoring, trouble shooting) are also presented. A digital and distributed control system is utilized for implementation. The distributed system has a flexible architecture compatible for each level of control sophistication. It offers simple function blocks for digital control of first-level loops, as well as, the higher levels without any need of computer programming.
Configuration Maps for Robot Path Planning in Two Dimensions
Authors: Red W. E. , Truong-Cao Hung-Viet
Published: July 2009

Graphically simulated “configuration maps” are used to plan manipulator paths in two-dimensions. Configuration maps represent a transformation of the Cartesian workspace into the manipulator joint coordinates, identifying both the free space and the space occupied by obstacles. Visual examination of the configuration map allows simulation users to plan collision-free paths by maneuvering the manipulators “point” along a series of path line segments which connect starting and final manipulator configurations. A PUMA 600 revolute manipulator experimentally verifies one such path planned through a congested workspace.
Coordination of Robots Sharing Assembly Tasks
Authors: Maimon O. Z. , Nof S. Y.
Published: July 2009

A multiple robot assembly cell for batch manufacturing is described and a new concept of an Activity Controller (AC) for such a cell is developed. The problem defined for the Activity Controller is which robot is to perform which operation, how, in terms of spatial routes and accessories, and when, in terms of timing and synchronization, in order to effectively achieve a certain task objective (e.g., minimize makespan time). The Activity Controller functions, structure, and algorithms for optimization and operational control are discussed, and then demonstrated on an actual assembly case.
Resolved Motion Adaptive Control for Mechanical Manipulators
Authors: Lee C. S. G. , Lee B. H.
Published: July 2009

This paper presents the development of a resolved motion adaptive control which adopts the ideas of “resolved motion rate control” [8] and “resolved motion acceleration control” [10] to control a manipulator in Cartesian coordinates for various loading conditions. The proposed adaptive control is performed at the hand level and is based on the linearized perturbation system along a desired hand trajectory. The controlled system is characterized by feedforward and feedback components which can be computed separately and simultaneously. The feedforward component resolves the specified positions, velocities, and accelerations of the hand into a set of values of joint positions, velocities, and accelerations from which the nominal joint torques are computed using the Newton-Euler equations of motion to compensate all the interaction forces among the various joints. The feedback component consisting of recursive least square identification scheme and an optimal adaptive self-tuning controller for the linearized system computes the perturbation torques which reduce the manipulator hand position and velocity errors along the nominal hand trajectory. The feasibility of implementing the proposed adaptive control using present day low-cost microprocessors is explored.
The Generalized Response of Servovalve-Controlled, Single-Rod, Linear Actuators and the Influence of Transmission Line Dynamics
Authors: Watton J.
Published: July 2009

The open-loop response of servovalve-controlled single-rod linear actuators in investigated for both the extending and retracting cases. A linearized frequency response technique is used to establish the probable type of dynamic behavior. Nondimensional results are presented as an aid to system design, and a boundary is established such that a simplified approximation may be used. A particular class of system is then examined where interconnecting transmission lines would be important, and the techniques previously used are modified accordingly. The techniques are verified with a precision actuator developed for fatigue testing of vehicle and airframe systems.
Industrial Robot Forward Calibration Method and Results
Authors: Whitney D. E. , Lozinski C. A. , Rourke J. M.
Published: July 2009

This paper presents a forward calibration method for serial link manipulators. The procedure uses a model whose parameters represent link lengths, joint encoder offsets, the relative orientations of consecutive axes, and experimentally observed effects of joint compliance, backlash, and gear transmission errors. A least squares numerical search algorithm uses theodolite measurements of tool position and the robot’s joint encoder readings to estimate the complete model’s parameters. The calibrated robot model predicts theodolite readings with an rms error of 5.7 × 10−5 rad (0.13 mm). Other tests show that this technique improves the robot model from as much as 4.8 mm error to 0.3 mm error.
Disturbance Accommodating Controllers for Rotating Mechanical Systems
Authors: Reinig K. D. , Desrochers A. A.
Published: July 2009

The use of magnetic bearings for supporting a rotor-shaft system has led to increasing interest in active control schemes. In this work, two disturbance accommodating controllers are developed which minimize the vibration of the system due to the mass imbalance of the rotor. The first controller generates an estimate of the disturbance force arising from this mass imbalance and then cancels its effect through the magnetic bearings. This keeps the rotor displacement at zero but often at the expense of high bearing forces. The second controller remedies this by estimating the eccentricity and then applying a force to the controlled shaft end to offset the effect of the eccentricity. This requires the controlled shaft end to follow a path so that the rotor shaft pivots about the center of mass. Thus, the center of mass of the system does not translate and so a disturbance force never occurs. Therefore, a small magnetic bearing force can be used to control the vibration of a large rotor. Both methods are compared to conventional bearing strategies.
Closed-Form Solutions for a Class of Optimal Quadratic Regulator Problems With Terminal Constraints
Authors: Juang Jer-Nan , Turner James D. , Chun Hon M.
Published: July 2009

Closed-form solutions are derived for coupled Riccati-like matrix differential equations describing the solution of a class of optimal finite time quadratic regulator problems with terminal constraints. Analytical solutions are obtained for the feedback gains and the closed-loop response trajectory. A computational procedure is presented which introduces new variables for efficient computation of the terminal control law. Two examples are given to illustrate the validity and usefulness of the theory.
A Model-Based Approach to Adaptive Control Optimization in Milling
Authors: Watanabe Tohru
Published: July 2009

An adaptive control optimization system using a model to represent actual physical phenomena in milling is discussed. The model is used for the identification of physical parameters, the calculation of the temperature at the tool edges, and the estimation of the tool wear rate. The shear angle of the shear plane, the flank wear land length of the tool edge, the true contact area at the flank wear land, the radial depth and the axial depth of cut are identified as the physical parameters, the shear stress, and the hardness of the work material from bending moments and torque in the spindle generated by the cutting force. The temperature at the flank wear land is calculated from identified parameters. The tool wear is represented theoretically as the summation of the thermal, mechanical and shock wears. Each wear is calculated from identified parameters and the temperature at the tool edges. Adaptive control experiments to keep the tool-wear rate at a constant value verify that the total system works well. An adaptive control optimization system using the tool-wear rate equation is compared with an adaptive control constraint system using Taylor’s tool life equation in a computer simulation. The simulation shows that adaptive control optimization gives higher cost efficiency than adaptive control constraint when the process parameters vary.
Exact Deadbeat Controller Design From N Impulse Response Samples
Authors: Rink R. E.
Published: July 2009

A simple method is given for the design of exact deadbeat regulators and PI controllers when only N impulse or step response samples from the process are available. It is required that the process be linear, controllable, observable, time invariant, and that N≥2n, where n is the degree of the process. It is not required that the process be open-loop stable, in distinction with previously-given simple methods. This makes it easy to include any number of integrations in the controller to achieve steady-state tracking properties of arbitrary type.
Pseudo-Decoupling and Control of Unidentified Plant
Authors: Thompson S.
Published: July 2009

A procedure based on measured step responses, is presented for the pseudo-decoupling of basically linear, nonoscillatory, multivariable plant. The method generates pre- and post-compensator matrices that will tend to make an otherwise nondominant plant diagonally dominant. Once this is achieved, each loop is then tuned on an individual basis using one of the classical on-line methods, thus eliminating the need for a model. The method is illustrated by means of two examples. The first demonstrates the design procedure and the second reports on the application of the method in controlling the power generated by an internal combustion engine.
Pressure Estimation From Oscillatory Signals Obtained Through BWR’s Instrument Lines
Authors: Akiyama Takao
Published: July 2009

Pressure signals obtained through a long skinny instrument line are usually disturbed because of fluid resonance oscillation. Therefore, such a problem is frequently encountered that an unperturbed pressure is desired to be estimated from the pressure signal. An estimation method consisting of a numerical inverse Laplace transformation was proposed to solve this problem. The validity of the method was evaluated for analytic models and an experimental system. This method was applied to the estimation of local pressures of a BWR nuclear power plant under transient tests.
The Use of Vector Techniques in Variational Problems
Authors: Everett L. J. , McDermott M.
Published: July 2009

A convenient means for applying vector mathematics to variational problems is presented. The total and relative variations of a vector are defined and results which follow from these definitions are developed and proved. These results are then used to express the variation of a functional using vector techniques rather than the classical scalar or matrix techniques. The simple problems of deriving equations of motion for a rigid body and for a rigid double pendulum are presented as examples of the technique. The key advantages of the method are that (1) it allows the investigator who is familiar and proficient with vector techniques to apply these skills to variational problems and (2) it greatly simplifies the application of variational techniques to problems which include both rigid body motions and elastic deformations. This is accomplished by providing the techniques necessary for computing the variation of a vector defined in a moving coordinate system without using coordinate transformations.
On Selecting Low Order Discrete-Time Modes Based on Dominant Energy Modes
Authors: Ouyang M. , Liaw C. M. , Pan C. T.
Published: July 2009

This brief proposes a simple criterion for selecting low order modes of discrete multivariable systems for model reduction. From the view point of power spectrum of the system output, the dynamic modes with dominant energy contributions instead of those with dominant eigenvalues will be retained. By using this criterion a simple model reduction procedure is developed. One advantage of this reduction technique is that the stability of the original system is preserved.
Extended Kalman Filter for Reconstruction of a Nonlinear Thermofluid System
Authors: Shoureshi R. , McLaughlin K.
Published: July 2009

Extended Kalman filter technique is used to develop an observer for a nonlinear thermofluid system, namely a heat pump. The observer’s optimal gain matrix is designed based on the eigenvalue distribution, integration time step, and stability of the system along a desired trajectory. The observer response is compared with experimental data and very good agreement is obtained.
Mechanical Behavior and Design Equations for Elastomer Shear Pad Remote Center Compliances
Authors: Whitney D. E. , Rourke J. M.
Published: July 2009

Commercially available Remote Center Compliances (RCC’s) are made with elastic elements called elastomer shear pads. If these pads are assumed to be linear two-component springs, it is easy to derive equations for the RCC’s composite elastic behavior. These equations can be quite incorrect, however, because the pads are in fact nonlinear six component springs. RCC performance equations incorporating models of real pad behavior are presented here, together with experimental verification. These show that real RCC’s have less stiffness and less compliance center projection than predicted by the linear models. A new design that overcomes these problems is also presented.
Time-Optimal Multistage Controllers for Nonlinear Continuous Processes
Authors: Johnson S. H. , Harlow D. G. , Yoon J. S.
Published: July 2009

The problem addressed is that of the online computational burden of gross-motion control laws for quick, strongly nonlinear systems like revolute robots. It will be demonstrated that a large amount of offline computation can be substituted for most of the online burden in cases of time optimization with constrained inputs if point-to-point specifications can be relaxed to cell-to-cell transitions. These cells result from a coarse discretization of likely swaths of state space into a set of nonuniform, contiguous volumes of relatively simple shapes. The cell boundaries approximate stream surfaces of the phase fluid and surfaces of equal transit times. Once the cells have been designed, the schedules of bang-coast-bang for the inputs are determined for all likely starting cells and terminating cells for various load conditions. The scheduling process is completed by treating all cells into which the trajectories might unexpectedly stray as additional starting cells. Then an efficient-to-compute control law can be based on the resulting table of optimal strategies.
Robust Bootstrap Method for Joint Estimation of States and Parameters of a Linear System
Authors: Puthenpura S. , Sinha N. K.
Published: July 2009

A robust version of the bootstrap method is presented for the joint on-line estimation of states and parameters of linear systems. Two feasible canonical forms for the state-space model are considered and compared. These state-space models are used in conjunction with the innovations model. The robustified estimation part of the bootstrap algorithm successfully handles the occasional large errors in the data, commonly called “outliers.” The convergence, rate of convergence, etc. of the proposed algorithm are theoretically established. To illustrate the potentiality of the suggested scheme, an example is also provided. Since the data available in real life are not devoid of errors, the robust bootstrap method is extremely useful in practical on-line applications.
Linearization and Sensitivity Models of the Newton-Euler Dynamic Robot Model
Authors: Murray J. J. , Neuman C. P.
Published: July 2009

Within the framework of the Newton-Euler formulation of robot dynamics, linearized and trajectory sensitivity models are constructed about a nominal trajectory. The approach illustrates the property that linearization of the O(N) recursive Newton-Euler formulation leads to O(N) recursive algorithms. These algorithms are conceived for simulation, parameter identification, and real-time control applications which require the numerical evaluation of the linearized or trajectory sensitivity models. The O(N) linearized recursive algorithms complement their O(N5) linearized Lagrange (Lagrange-Euler) counterparts which are conceived for physical insight, and manipulator and controller design.
A Rotary Magnetic Damper Consisting of Several Sector Magnets and an Arbitrarily Shaped Conductor With a Circular Cavity
Authors: Karube Yasuo , Nagaya Kosuke
Published: July 2009

In this paper, the damping force and the damping coefficient of a rotary magnetic damper consisting of several sector magnets and an arbitrarily shaped plate conductor with a circular cavity have been obtained theoretically. The unit step function is applied to solve the differential equations of the electromagnetic field, and the boundary condition of the outer arbitrarily shaped boundary of the plate conductor is satisfied directly by making use of the Fourier expansion collocation method. Numerical calculations have been carried out for the dimensionless damping coefficients with the variations of various factors such as the magnetic flux range, the outer shape and the radius of the inner circular cavity of the conductor, the position and the number of the magnets.
A Method of Model Reduction
Authors: Lin Jium-Ming , Han Kuang-Wei
Published: July 2009

In this brief note, the effects of model reduction on the stability boundaries of control systems with parameter variations, and the limit-cycle characteristics of nonlinear control systems are investigated. In order to reduce these effects, a method of model reduction is used which can approximate the original transfer function at S=0, S=∞, and also match some selected points on the frequency response curve of the original transfer function. Examples are given, and comparisons with the methods given in current literature are made.
The Dynamic Performance of an Electrohydraulic Servovalve/Motor System With Transmission Line Effects
Authors: Watton J.
Published: July 2009

The transient response of an electrohydraulic servovalve coupled to an axial piston ball motor is analyzed. In particular, the effect of long lines between the servovalve and motor is studied together with coulomb friction effects at the motor. The dynamic characteristics of the basic system with short lines is first established via frequency response measurements coupled with a small signal linearized analysis. Longer lines are then added and the method of characteristics, coupled with a quasi-analytical solution for the motor-end equations, is used to predict the large signal transient response. The importance of coulomb friction damping is established together with damping due to servovalve dynamics.
The Effect of Drain Orifice Damping on the Performance Characteristics of a Servovalve Flapper/Nozzle Stage
Authors: Watton J.
Published: July 2009

The effect of a return line orifice on the steady-state performance and dynamic characteristics of a servovalve flapper/nozzle stage is investigated. Generalized design characteristics are initially developed and a specific application is then pursued by including torque motor dynamics. The possible cause of high frequency whistle within such systems is then discussed. A sufficient condition for valve whistle is established and shown to be critically dependent upon the supply pressure.
Control of Industrial Manipulators With Bounded Uncertainties
Authors: Shoureshi R. , Corless M. J. , Roesler M. D.
Published: July 2009

Present on-line control schemes for robotic manipulators require high computing power to perform real-time estimation and adaptation and/or an exact model of the manipulator. These requirements result in impractical control schemes for real industrial manipulators. This paper presents a new robust tracking control technique for industrial manipulators in the presence of various uncertainties. It does not require an exact model of the manipulator and it compensates for uncertainties in the system dynamics, such as friction, and uncertain inputs including load variations. The controller consists of two portions: one for the nominal part of the system, and the other portion for uncertainties compensation. This control scheme is simulated for a General Electric P50 robot and the results are presented.