bluuebunny/crossref_metadata_2025 huggingface dataset:
The Through-Thickness Compressive Strength of a Composite Sandwich Panel With a Hierarchical Square Honeycomb Sandwich Core
Authors: Côté F. , Russell B. P. , Deshpande V. S. , Fleck N. A.
Published: July 2009

Sandwich panels with aluminum alloy face sheets and a hierarchical composite square honeycomb core have been manufactured and tested in out-of-plane compression. The prismatic direction of the square honeycomb is aligned with the normal of the overall sandwich panel. The cell walls of the honeycomb comprise sandwich plates made from glass fiber/epoxy composite faces and a polymethacrylimide foam core. Analytical models are presented for the compressive strength based on three possible collapse mechanisms: elastic buckling of the sandwich walls of the honeycomb, elastic wrinkling, and plastic microbuckling of the faces of the honeycomb. Finite element calculations confirm the validity of the analytical expressions for the perfect structure, but in order for the finite element simulations to achieve close agreement with the measured strengths it is necessary to include geometric imperfections in the simulations. Comparison of the compressive strength of the hierarchical honeycombs with that of monolithic composite cores shows a substantial increase in performance by using the hierarchical topology.
Theoretical Analysis of Transmission Error in Helical Synchronous Belt With Error on Belt Side Face Under Bidirectional Operation
Authors: Kagotani Masanori , Ueda Hiroyuki
Published: July 2009

Synchronous belt drives are occasionally required to transmit rotation accurately and are often employed in bidirectional operation. For transmission error per single pitch of the pulley, a helical synchronous belt with a helix angle of the tooth trace is effective. However, this belt causes axial movement because of the axial belt tooth load. When the belt comes into contact with the pulley flange or the belt moves away from the pulley flange due to bidirectional operation, the accuracy of finishing on the belt side face affects the transmission error. In the present study, the transmission error considering the error on the belt side face in a helical synchronous belt drive that uses flanged pulleys under the quasistatic condition and transmitted torque was investigated theoretically and experimentally for the case in which the pulley was rotated in bidirectional operation. The calculated transmission error coincided well with the experimentally obtained transmission error. Under forward rotation, the transmission error having a period of one rotation of the belt is caused by the error on the belt side face when the belt comes into contact with the pulley flange. Under reverse rotation, the transmission error is generated by a change in the belt tension due to the application of a transmitted torque and by the difference in axial belt movements between the driving and driven sides when the belt moves away from the pulley flange.
A Note on the Derivation of Plane-Strain Elastic Green’s Functions for Bimaterial Solids
Authors: Zhang Xi
Published: July 2009

This brief note presents a rigorous proof of the general solutions obtained by Aderogba [1977, “On Eigenstresses in Dissimilar Media,” Philos. Mag., 35, pp. 281–292] for a defect in elastic bimaterial solids. The derivation is based on the fact that some derivative and integral forms of the biharmonic functions are also biharmonic. The associated solutions can be expressed as the linear combinations of these biharmonic functions and their unknown coefficients can be determined by the interface conditions. It is found that the coefficients only depend on the contrasts of material constants across the interface.
An Accurate Low Dimension Model for the Waves on Thin Layer Fluid Flowing Down an Inclined Plane
Authors: Abderrahmane H. Ait , Vatistas G. H.
Published: July 2009

This technical brief deals with the surface instability mode of a liquid film flowing down an inclined plane. A four-equation model that describes the development of the film depth, the flow rate, the free-surface velocity, and the wall shear stress is proposed. The obtained results were found to be in very good agreement with experimental and theoretical results of Liu et al. (1993, “Measurements of the Primary Instability of Film Flow,” J. Fluid Mech., 250, pp. 69–101) and Brevdo et al. (1999, “Linear Pulse Structure and Signalling in Film Flow on an Inclined Plane,” J. Fluid Mech., 396, pp. 37–71).
Elasticity Approach to Load Transfer in Cord-Composite Materials
Authors: Paris Anthony J.
Published: July 2009

An elasticity approach to the mechanics of load transfer in cord-reinforced composite materials is developed. Finite cords embedded in an elastic matrix and subjected to axial loading is considered, and the extension-twist coupling of the cords is taken into account. Closed form solutions for the axial force and twisting moment in the cord, the shear stresses at the cord-matrix interface in the axial and circumferential directions, the effective axial modulus of the cord, and the apparent modulus of the cord composite are presented. An example of a cord composite typical of what can be found in steel-belted-radial tires is used to illustrate the results. It was found that large shear stresses occur at the cord-matrix interface in both the axial and circumferential directions at the cord ends and that the effective modulus of the cords may be greatly reduced. As a result, the apparent modulus of the composite may be significantly less than that found by a conventional application of the rule-of-mixtures approach.
One-Way and Two-Way Coupling Analyses on Three Phase Flows in Hydrocyclone Separator
Authors: Mousavian S. M. , Ahmadvand M. , Najafi A. F.
Published: July 2009

The flow behavior in hydrocyclones is quite complex. The computational fluid dynamics method was used to simulate the flow fields inside a hydrocyclone in order to investigate its separation efficiency. In the computational fluid dynamics study of hydrocyclones, the air-core dimension is a key to predicting the mass split between the underflow and overflow. In turn, the mass split influences the prediction of the size classification curve. Generally in hydrocyclone simulations, assuming low particle volume fractions, the discrete phase effects on the continuous phase have been excluded; therefore, one-way coupling method has been used. Due to high particle consistencies, regions in some cases, especially in underflow areas, excluding discrete phase effects on continuous phase may be ineligible. In this study for an example case by consisting discrete phase effects and using two-way coupling method, simulation accuracy noticeably has been improved. Three models, the k−ε model, the Reynolds stress model (RSM) without considering air core, and Reynolds stress turbulence model with volume of fluid multiphase model for simulating air core, were compared for the predictions of velocity, axial, and tangential velocity distributions and separation proportion. Results by the RSM with air-core simulation and two-way coupling model, since it produces some detailed features of the turbulence and discrete phase mode effects, are clearly closer in predicting the experimental data than the other two.
Antiplane Harmonic Elastodynamic Stress Analysis of an Infinite Wedge With a Circular Cavity
Authors: Liu Gang , Ji Baohua , Chen Haitao , Liu Diankui
Published: July 2009

In this paper, the antiplane harmonic dynamics stress of an infinite isotropic wedge with a circular cavity is analyzed for the first time by using a novel method with Green’s function, complex functions, and multipolar coordinates. A basic solution for the displacement field of an elastic half-space containing a circular cavity subjected to antiplane harmonic point force is employed as the Green’s function. Based on the Green’s function, the infinite wedge problem is equivalently transformed into the problem of a half-space divided by a semi-infinite traction free line. The equivalent problem is solved numerically to determine the dynamic stress field in the wedge at different apex angles and cavity locations. We show that the wedge angle, cavity location, and incident angle and frequency of the external load have significant effect on the dynamic stress of the cavity surface. The dynamic stress concentration factor on the cavity surface becomes singular when the cavity is close to the boundary of the wedge.
Energy Dissipation in
Normal Elastoplastic Impact Between Two Spheres
Authors: Du Yanchen , Wang Shulin
Published: July 2009

Elastoplastic deformation occurs widely in engineering impact. Although many empirical solutions of elastoplastic impact between two spheres have been obtained, the analytical solution, verified by means of other methods, to the impact model has not been put forward. This paper proposes a dynamic pattern of elastoplastic impact for two spheres with low relative velocity, in which three stages are introduced and elastic and plastic regions are both considered. Finite element analyses with various parameters are carried out to validate the above model. The numerical results prove to agree with the theoretical predictions very well. Based on this model, the dissipation nature of elastoplastic impact are then analyzed, and the conclusion can be drawn that materials with lower yield strength, higher elastic modulus, and higher mass density have better attenuation and dissipation effects. The study provides a basis to predict the particle impact damping containing plastic deformation and to model the impact damped vibration system enrolling microparticles as a damping agent.
Pointwise Identification of Elastic Properties in Nonlinear Hyperelastic Membranes—Part I: Theoretical and Computational Developments
Authors: Lu Jia , Zhao Xuefeng
Published: July 2009

We present an innovative method for characterizing the distributive elastic properties in nonlinear membranes. The method hinges on an inverse elastostatic approach of stress analysis that can compute the wall stress in a deformed convex membrane structure using assumed elastic models without knowing the realistic material parameters. This approach of stress analysis enables us to obtain the wall stress data independently of the material in question. The stress and strain data collected during a finite inflation motion are used to delineate the elastic property distribution in selected regions. In this paper, we discuss the theoretical and computational underpinnings of the method and demonstrate its feasibility using numerical simulations involving a saclike structure of known material property.
Pointwise Identification of Elastic Properties in Nonlinear Hyperelastic Membranes—Part II: Experimental Validation
Authors: Zhao Xuefeng , Chen Xiaolin , Lu Jia
Published: July 2009

Following the theoretical and computational developments of the pointwise membrane identification method reported in the first part of this paper, we perform a finite inflation test on a rubber balloon to validate the method. The balloon is inflated using a series of pressurized configurations, and a surface mesh that corresponds through all the deformed states is derived using a camera-based three dimensional reconstruction technique. In each configuration, the wall tension is computed by the finite element inverse elastostatic method, and the in-plane stretch relative to a slightly pressurized configuration is computed with the aid of finite element interpolation. Based on the stress-strain characteristics, the Ogden model is employed to describe the material behavior. The elastic parameters at every Gauss point in a selected region are identified simultaneously. To verify the predictive capability of the identified material model, the deformation under a prescribed pressure is predicted using the finite element method and is compared with the physical measurement. The experiment shows that the method can effectively delineate the distributive elastic properties in the balloon wall.
A Slip Damping Model for Plasma Sprayed Ceramics
Authors: Torvik Peter J.
Published: July 2009

Ceramic materials applied by air plasma spray are used as components of thermal barrier coatings. As it has been found that such coatings also dissipate significant amounts of energy during vibration, they can also contribute to reducing the amplitude of resonant vibrations. In order to select a coating material for this purpose, or to adjust application parameters for increased dissipation, it is important that the specific mechanism, by which such dissipation occurs, be known and understood. It has been suggested that the dissipative mechanism in air plasma sprayed coatings is friction, along interfaces arising from defects between and within the “splats” created during application. An analysis, similar to that for the dissipation in a lap joint, is developed for an idealized microstructure characteristic of such coatings. A measure of damping (loss modulus) is extracted, and the amplitude dependence is found to be similar to that observed with actual coating materials. A critical combination of parameters is identified, and variations within the microstructure are accounted for by representing values through a distribution. The effective or average value of the storage (Young’s) modulus is also developed, and expressed in terms of the parameters of the microstructure. The model appears to provide a satisfactory analytical representation of the damping and stiffness of these materials.
Creeping Flow of Phan-Thien–Tanner Fluids in a Peristaltic Tube With an Infinite Long Wavelength
Authors: Abd El Naby Abd El Hakeem
Published: July 2009

In this study both linearized and the exponential forms of the Phan-Thien–Tanner model (PTT) are used to simulate the peristaltic flow in a tube. The solutions are investigated under zero Reynolds number and infinitely long wavelength assumptions. Computational solutions are obtained for pressure rise and friction force. The results of the average chyme velocity in the small intestine show that the PTT model is in good agreement with the experimental results, as shown in Table 1. Also, the magnitude of pressure rise and friction force of the exponential PTT model are smaller than in linear PTT model for different values of flow rate. The peristaltic pumping and the augmented pumping are discussed for various values of the physical parameters of interest. The pressure rise and friction force of PTT were compared with other studies in both Newtonian and non-Newtonian cases.
Parameter Estimation of Delay Systems Via Block Pulse Functions
Authors: Shin Yen-Ping , Hwang Chyi , Chia Wei-Kong
Published: July 2009

Linear time-invariant delay-differential equation systems are approximately represented by a set of linear algebraic equations with the block pulse functions. A least squares estimate is then used to determine the unknown parameters. Examples with satisfactory results are given.
A First Principles Model for Steam Turbine Control Analysis
Authors: Kalnitsky K. C. , Kwatny H. G.
Published: July 2009

A first principles model of a steam turbine is presented. Its intended use is to aid the design and analysis of control systems in which thermal and fluid interactions between the turbine and balance-of-plant are of primary concern. Thus the focus is representation of aggregate steam flow dynamics. Modeling of individual governor valve flow characteristics as well as an algorithm for representing governor valve overlap are two distinguishing factors of this model.
Volterra Series Expansion for Bilinear Systems in a Nonlinear Feedback Loop
Authors: Bertuzzi A. , Bruni C. , Gandolfi A. , Germani A.
Published: July 2009

In this paper the class of distributed bilinear systems in a nonlinear feedback loop is considered. First of all the existence and uniqueness of solution is stated when input and state belong to L2 spaces. Then the existence of the Volterra series expansion for the input-output map is proved for inputs in any sphere around the origin; the proof is based on a new version of the Weierstrass approximation theorem.
A High Order, Lumped Parameter, Jet Dynamic Model for the Frequency Response of Laminar Proportional Amplifiers
Authors: Drzewiecki T. M.
Published: July 2009

This paper presents a high-order, lumped parameter, jet-dynamic model for laminar proportional amplifiers (LPA’s). The governing equations for the lumped-parameter representation of the flow regimes found in the input of an LPA are derived in the Laplace domain, and an equivalent electrical circuit is obtained. The input governs the overall response of the LPA and may be modeled in its simplest form by five reactive components. The transmission of the signal from input to output is delayed by a transport time (determined by observation of flow visualization of a step response) equal to twice the average particle transit time. A pressure difference is then developed at the splitter that is proportional to the loading and the vent conditions. This signal is acoustically fed back to the control region of the jet, augmenting jet deflection when in phase. The vent inductance is found to have a significant influence on the low-frequency gain. Resonant regions determined by this model correspond closely to edgetone eigenfrequencies reported in the literature. Experimental data have shown good agreement with theory for the amplitude frequency response of LPA’s and excellent agreement for the phase shift. An engineering guide developed for the bandpass characteristics of LPA’s indicates that operating bandwidths of up to 14 kHz can be expected for amplifiers with a nozzle width of 0.25 mm, and ultrasonic operation appears feasible with devices having nozzle widths as large as 0.1 mm.
Fluidics in Aircraft Engine Controls
Authors: Davies G. E.
Published: July 2009

Fluidics is a particularly appropriate technology for engine controls as it is capable of measuring pressure ratio, one of the basic engine performance parameters, as a fundamental quantity. This results in improved accuracy of measurement and obviates the need of conventional systems to utilize nonoptimum, but easier to measure, control parameters. A wide range of aircraft engine controls has been developed covering controls for compressor inlet guide vanes, compressor bleed valves, engine fuel flow including engine instrumentation. Total fluidic unit deliveries exceed 4200 and the civil operating hours exceed 13.5 million. As a further development, a completely fluidic engine control system is proposed with an electronic computer controlled secondary control or trim system for efficiency optimization.
Linear Fluid Resistance Using Switching Valves and a Tank
Authors: Katz S. , Svoboda J. V. , Somji M.
Published: July 2009

An active linear fluid resistance is demonstrated using the switched capacitor concept from electronics. For the analogous fluid component, this requires using switching valves to alternately fill and empty a tank. Analysis shows that the equivalent linear resistance is directly proportional to the switching period and inversely proportional to the tank capacitance. For fluid components, the linearity is restricted to those cases where complete filling and emptying is achieved. The time period required to insure linearity is derived in terms of fluid circuit variables. As a result, there is a lower limit on the magnitude of resistance that can be obtained for a given fluid circuit. This magnitude depends on circuit component values, as well as on the desired operating pressure range. However, the net result is that we may construct a linear fluid resistance that has no dependence on orifice sizes, discharge coefficients, or Reynolds number. The experimental fluid circuit contains a source volume in addition to the switching values and tank required for the resistance component. The source volume filters the transients and permits steady state measurements. Experiments are performed for resistances with different switching periods and tank volumes. The experimental resistance values are always within 5 percent of the theoretical predictions. The switched capacitor concept may prove useful in the design of mass flowmeters, frequency-to-analog converters, electric-to-pneumatic transducers, and temperature sensors.
Discrete-Time Equivalent of Continuous-Time Filtering Processes
Authors: Friedland Bernard
Published: July 2009

The continuous-time Kalman filtering problem over a finite time interval can be made equivalent to a discrete-time filtering problem. The matrices in the latter are related to the submatrices of the transition matrix of a Hamiltonian system that corresponds to the continuous-time filtering problem.
Prediction of the Probability of Rail Vehicle Derailment During Grade Crossing Collisions
Authors: Cherchas D. B. , English G. W. , Ritchie N. , McIlveen E. R. , Schwier C.
Published: July 2009

A mathematical model and digital computer simulation are developed to analyze the dynamics of railway and road vehicles during grade crossing collisions. The main objective of the simulation is to relate the probability of derailment to railway vehicle speed; however, a variety of other response characteristics such as railway and road vehicle structure deformation and road vehicle dynamic response can be examined. The criterion for derailment is based on the derailment coefficient, i.e., ratio of wheel flange/railhead lateral force to vertical wheel load. More specifically, the computer simulation utilizes a relationship between the probability of wheel climb commencing and the derailment coefficient, established by Japan National Railways based on their experimental test program. A preliminary investigation is made of the sensitivity of the derailment probability to various collision situations, with the emphasis on increasing rail vehicle speed. Conclusions and recommendations based on this analysis are presented.
Optimal Control of a Class of Discrete Multivariable Nonlinear Systems. Application to a Fermentation Process
Authors: Gallegos Joaqui´n Alvarez , Gallegos Jaime Alvarez
Published: July 2009

The optimal control of a class of discrete multivariable nonlinear systems given by: xk+1 = a (xk) + B (xk) uk, yk = C xk, is analyzed. A closed-loop structure is obtained with the proposed performance index. The addition of numerical integrators to the output error and the design of an optimal control law for the resultant augmented system lead to a very robust control structure. The performance of this control law is evaluated by applying it to a simulated continuous culture fermentation process.
A Stress Model for Lumber Drying Control
Authors: Lessard R. A. , Limbert D. E. , Pokoski J. L. , Hill J. L.
Published: July 2009

Rapid changes in lumber value and energy costs have forced concern for more efficient lumber drying and a higher quality end product. Computer automation provides a practical solution to this problem. Mathematical predictions of moisture loss and shrinkage induced stress are required for effective automation. In response to this need an elastic-plastic hysteresis stress model to predict stresses in boards during kiln drying was developed. The model prediction is compared to experimental data for release strain, set strain, prong deflection, and board failures.
Frequency Response Analysis of an Ocean Wave Energy Converter
Authors: Masubuchi M. , Kawatani R.
Published: July 2009

A theoretical analysis is presented for the dynamic behavior and energy conversion efficiency of a wave energy converter which is oscillating and absorbing power in an incident sinusoidal wave train. The energy converter consists of two floating bodies which have different configuration and are connected by a rigid link. Basic equations governing the floating bodies contained in the energy converter are obtained by assuming two dimensional motions and by considering the interactions between the two bodies and hydrodynamic and damping forces, and they have been solved numerically by using Lewis form as the configuration of the floating bodies. Energy absorption is assumed to be proportional to the square of the relative velocity between the oscillating body and the connecting link. It is shown that nearly 100 percent of wave energy is converted into mechanical energy in a wide frequency band.
Noninvertible Digital Transfer Functions Arising From Minimum Phase Analog Process Models
Authors: Neuman C. P. , Morris R. L.
Published: July 2009

Current approaches to discrete model reference adaptive control (MRAC) [1–6] require the inverse of the discretized process model to achieve the desired model following. The objective of this paper is to illustrate that the step-invariant transformation of a minimum phase, physical analog process model (based upon a machine tool position controller) leads to a nonminimum phase discrete-time model and thus precludes the possibility of obtaining a stable inverse for the discrete-time process model. This example illustrates the shortcomings of applying discrete MRAC to higher-order processes and indicates the need for alternative MRAC approaches which do not require the adaptive cancellation of process zeros.
A Modified Algorithm for the Least Squares Identification
Authors: Batur C.
Published: July 2009

To identify the dynamics of mechanical systems, the usual practice is to assume a certain model structure and try to estimate the unknown parameters of this model on the basis of input output observations. For mechanical systems operating under noisy industrial conditions, the number of unknowns of the problem exceeds the number of equations available. It is then inevitable that certain assumptions must be made on the unknown disturbances. This paper assumes that the only reliable feature of the disturbance is its independence of input. This yields a set of assumptions in excess of the minimal requirements and an endeavor has been made to exploit this excess to minimize the parameter estimation errors. Th resulting algorithm is similar to that of the Two Stage Least Squares method [1].
Optimal Control of Linear Distributed Parameter Systems by Shifted Legendre Polynomial Functions
Authors: Wang Maw-Ling , Chang Rong-Yeu
Published: July 2009

The optimal control problem of a linear distributed parameter system is studied by employing the technique of shifted Legendre polynomial functions. A partial differential equation, which represents the linear distributed parameter system, is expanded into a set of ordinary differential equations for coefficients in the shifted Legendre polynomial expansion of the input and output signals. Expressing the performance index in terms of the expansion coefficients, we transformed an optimal control gain problem into a two point boundary value problem by applying the maximum principle. The two-point boundary value problem is reduced into an initial value problem, the solution of which can be easily obtained by the proposed computational algorithm. An illustrative example will be used to prove this point.
Centrifugal Compressor Supervisory Control for Building Automation Systems
Authors: Cherchas D. B. , Abdelmessih A. , Townsend M.
Published: July 2009

Optimal control strategies suitable for implementation on a supervisory digital computer controller are developed to maximize the coefficient of performance of the centrifugal compressor subsystem for a building central cooling plant. The analytical determination of the optimum strategies is based on models, determined from experimental data, of the power consumption of the centrifugal compressor subsystem components. The supervisory control strategies determine optimum set points for the evaporator entering and leaving water temperatures, condenser leaving water temperature and the storage tank return water temperature. Cost function values are given for a range of system parameters.
Control Law Design and Dynamic Evaluations for a Maglev Vehicle With a Combined Lift and Guidance Suspension System
Authors: Kortu¨m W. , Utzt A.
Published: July 2009

For a magnetically levitated vehicle (MAGLEV) with a combined lift and guidance system using u-shaped electro-magnets control law design based on simplified (design) models and dynamic simulations with more complex (evaluation) models are treated. It is demonstrated, that, even in view of the coupling of lateral (guidance) and vertical (lift) modes, caused by the inclined magnets, it is still possible to design the control law from a vertical model only. The control design is performed by quadratic synthesis (RICCATI design), because the given design spefifications can be most easily translated into performance criteria of this type. The dynamic evaluations, which are carried through with a general purpose vehicle simulation program, show—with a minor extension for one lateral mode (yaw)—that above strategy yields good results meeting all dynamic specifications. Especially, the lateral response—not considered in the design—due to wind gusts is well damped and also the vertical response due to track irregularities and track flexibility is well behaved and stable.
Modeling and Control of a Refrigerant Evaporator
Authors: Gruhle W.-D. , Isermann R.
Published: July 2009

Based on the balance equations for enthalpy, mass, and momentum a theoretical model of a refrigerant evaporator has been developed. The distributed parameter process is approximated by several lumped parameter models. The model is completed by equations for the expansion valve, the compressor and the superheater. Various effects, e.g., the random fluctuations of the liquid-dry-out-point can be explained by the model. The dynamic behavior of the evaporator is investigated as a function of the manipulating signal UEV (position of the expansion valve) and various disturbances (air temperature ϑA, condenser pressure pCd and compressor rotation speed nc), considering the superheating temperature ϑs as control variable and the evaporator performance Q˙E, which has to be optimized. Two controllers are considered. First, the control behavior with a conventional thermostatic expansion valve is shown, which often operates unstable. The control performance can be considerably improved by a controller whose structure and parameters are better adapted to the evaporation process. For the experiments a process computer is connected on-line to the process. It will be demonstrated that the performance of the evaporator and therefore its efficiency can be increased by at least 5 percent.
Fuel-Air Ratio Determination From Cylinder Pressure Time Histories
Authors: Gilkey J. C. , Powell J. D.
Published: July 2009

Determining fuel-air ratio quickly over a wide range of engine operating conditions is desirable for better transient engine control. This paper describes a method based on cylinder pressure time history pattern recognition which has potential for providing such a high bandwidth measurement. The fact that fuel-air ratio has an effect on the shape of the cylinder pressure trace is well-known. It should therefore be possible to obtain the fuel-air ratio of an engine by examining the pressure trace if the engine speed, load, and EGR are known. The difficulty lies in separating the effects of unknown engine load, speed, and EGR from the fuel-air ratio effects. An algorithm was developed using a wide range of steady state experimental data from a single cylinder engine. Application of the algorithm requires the calculation of first, second and third moments of the cylinder pressure time history. Verification of the algorithm showed that the root mean square error in estimates were about 5 percent for fuel-air ratio and 3 percent for a combination of fuel-air and EGR. These results were obtained using a single pressure trace which yields a response time of 1.5 engine revolutions. The algorithm was also found to be relatively insensitive to the use of different fuels, errors in spark advance, and variations in relative humidity. Research is continuing to verify the accuracy under transient engine conditions. An operational count shows that this algorithm should be well within the limits of present microprocessor technology.
Representation of Measured Ejector Characteristics by Simple Eulerian Bond Graph Models
Authors: Paynter H. M.
Published: July 2009

Ejectors (or jet pumps) are highly reliable pure fluidic devices very commonly used in power plants, propulsion systems, petrochemical processes and other thermofluid systems. However, little off-design data has been available in a form suitable for dynamic simulation and control system design. Fortunately, concerns of the nuclear industry have recently led the Idaho National Engineering Laboratory (INEL) to obtain, from their LOFT Test Support facility, ejector test data sufficiently extensive to formulate a complete model accurately describing all flow conditions. Thus an elementary fixed-constant bond graph structure will approximate complete ejector characteristics, while a model only slightly more complex fits all INEL data within experimental scatter.
Steady-State Covariance Analysis for a Forward-Pass Fixed-Interval Smoother
Authors: Watanabe Keigo
Published: July 2009

This paper studies the solution of the steady-state error covariance equation (which is represented by the algebraic Lyapunov equation) associated with a forward-pass fixed-interval smoother for discrete-time linear systems. A necessary and sufficient condition is given to assure the existence of a unique stabilizing solution. A simple algorithm for solving such an equation is also proposed by using four eigenvector matrices, which are generated by a symplectic matrix, corresponding to the algebraic Riccati equation of a backward-pass information filter. Thus the results have application to the important problem of the limiting covariance analysis of smoothing prior to practically dealing with a finite interval of data.
Automated Symbolic Derivation of Dynamic Equations of Motion for Robotic Manipulators
Authors: Leu M. C. , Hemati N.
Published: July 2009

A general computer program for deriving the dynamic equations of motion for robotic manipulators using the symbolic language MACSYMA has been developed. The program, developed based on the Lagrange formalism, is applicable to manipulators of any number of degrees of freedom. Examples are given to illustrate how to use this program for dynamic equation generation. Advantages of expanding the dynamic equations into symbolic form are presented. Techniques for improving efficiency of equation generation, overcoming computer memory limitation, and approximating manipulator dynamics are discussed.
Control of Elastic Robotic Systems by Nonlinear Inversion and Modal Damping
Authors: Singh S. N. , Schy A. A.
Published: July 2009

Energy efficient, lightweight robot arms for space applications have considerable structural flexibility. For large and fast motions, both the nonlinear coupled dynamics and the elastic behavior of the robots must be considered in control system designs. This paper presents an approach to the control of a class of flexible robotic systems. A control law is derived which decouples the joint-angle motion from the flexible motion and asymptotically decomposes the elastic dynamics into two sub-systems, representing the transverse vibrations of the elastic link in two orthogonal planes. This decomposition allows the design of an elastic mode stabilizer independently based on lower order models representing structural flexibility. The closed-loop system is shown to be globally asymptotically stable and robust to uncertainty in system parameters. Simulation results are presented to show that large, fast control of joint angles can be performed in spite of space vehicle motion and uncertainty in the payload.
Current Monitoring of Field Controlled DC Spindle Drives
Authors: Stein J. L. , Shin Kyung-Chul
Published: July 2009

Unmanned machine tools as part of an automated factory require reliable inexpensive sensors to provide machine and process information. The electric current in the DC motor of a CNC machine tool can be inexpensively measured and used to calculate loads on the drive system. To characterize the bandwidth, sensitivity and accuracy of current monitoring on a DC field controlled spindle drive 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 when the spindle system is operated above the base speed. Tests were conducted to determine the model’s parameters and to verify the model. The bandwidth and sensitivity of this sensor are shown to be spindle speed dependent. High speeds improve sensitivity and reduce bandwidth. Sensitivity and bandwidth vary by factors of 4.3 and 18.5, respectively, over the speed range. The signal to noise ratio is limited by external load induced variations in the spindle system friction. Recommendations concerning machine designs and process operating conditions to improve current monitoring on spindle drives are presented.
Pole Placement Methods for Multivariable Control of Robotic Manipulators
Authors: Norcross R. J. , Wang J. C. , McInnis B. C. , Shieh L. S.
Published: July 2009

Efficient methods for multivariable digital control of robotic manipulators based upon pole placement by state feedback are presented as an improved method of path control. Implementation of these methods by both gain scheduling and on-line computation is discussed. An example of the computations for a three-link robot arm and computer simulation experiments are given.
Optimal Observers Using Time-Weighted Performance Index With Prespecified Eigenvalues
Authors: Kwon Bong-Hwan , Youn Myung-Joong
Published: July 2009

In this paper, the design problem of an optimal observer minimizing a given time-weighted quadratic performance index is considered when the eigenvalues of the observer are prespecified. Necessary conditions for an optimality of the observer that satisfies eigenvalues constraint are derived and a numerical example is given to show the effect of a time-weighted quadratic performance index on the transient responses of the estimate error.
Improved Identification of Mechanical Multibody Systems From Discrete-Time Data. Differential Identification of Linear Mechanical Systems
Authors: Roether F.
Published: July 2009

The parameter estimation problem of linear mechanical systems evaluating discrete-time data is considered. In principle it can be solved by the algebraic back-transformation of an estimated discrete time model. This approach means that a-priori-knowledge concerning some physical parameters or zero positions in the matrices of the mechanical system cannot be used. An algorithm is presented which offers a possibility to use this information. It requires initially an approximate discrete-time model-parametrization, generated e.g., with known identification schemes. The new method combines data transformation based on linearized algebraic links between continuous and discrete-time models with a side-constrained instrumental variable estimator. Simulation results from a centrifuge model, illustrating the improved accuracy of the estimates if continuous built-in a-priori information are available.
Guaranteed Asymptotic Output Stability for Systems With Constant Disturbances
Authors: Schmitendorf W. E. , Barmish B. R.
Published: July 2009

For a class of linear systems in which there are uncertain parameters in the system and input matrices, as well as constant additive disturbances, a linear state feedback control law is derived. The only information available about the uncertain parameters is the bounding sets in which they lie. The design guarantees that the specified output approaches zero for all possible parameter values and for all initial conditions. Two examples illustrate the application of the theory.
Investigation of an Electrohydraulic Servovalve With Tuneable Return Pressure and Drain Orifice
Authors: LeQuoc S. , Cheng R. M. H. , Limaye A.
Published: July 2009

This paper describes a new concept of electrohydraulic servovalve where the novelty lies mainly in the fact that the return pressure and return orifice of the servovalve are tuneable and can be adjusted to satisfy the system control requirements. The actuator velocity characteristics of a hydraulic servomechanism operating under steady state condition is analysed through the use of dimensionless quantities. It is established that the proposed configuration exhibits a nonlinear actuator velocity versus servovalve opening relationship and at small servovalve opening, the system offers a higher actuator velocity. The closed loop system transient responses are also investigated by means of digital computer simulation. The results are experimentally verified on a test rig specifically designed for this purpose. It is observed that with the return pressure and return orifice properly tuned, one can achieve a high gain yet high damping servosystem. A design procedure is described which provides the designer with a step by step method for determining the tuning parameters in order to obtain a desired system performance.
Stable Reduction of Linear Discrete-Time Systems Via a Multipoint Tangent Phase CFE
Authors: Hwang Chyi , Chen Muh-Yang
Published: July 2009

This paper presents a procedure of linear discrete-time system reduction via a multipoint tangent phase continued-fraction expansion (CFE). The model reduction approach followed starts by transforming the z-domain tangent phase function into the u-domain one using the u-transformation u = z−1 + z. Subsequently, the u-domain tangent phase function is expanded into a multipoint continued fractions. The desired reduced z-transfer function is finally obtained by factorizing the truncated and inverted u-domain multipoint tangent phase CFE approximant. The main feature of the proposed method is that it not only guarantees the stability but also gives good overall approximations to both frequency and time responses of the given system.
Multivariable Disturbance Rejection Tracking Controllers for Systems With Slow and Fast Modes
Authors: Jayasuriya Suhada
Published: July 2009

In this paper we consider the design of controllers for a class of singularly perturbed multi-input-multi-output linear time-invariant systems where the objective is asymptotic tracking in the presence of persisting disturbances. The controller structure consists of a precompensator and a stabilizing compensator used in conjunction with a full order observer. Singular perturbation methods are used to obtain various components of the control system so that numerical ill conditioning is avoided. The design procedure is illustrated by synthesizing a controller for a second order singularly perturbed plant.
A Control Theoretic Study on Dynamical Biped Locomotion
Authors: Miyazaki Fumio , Arimoto Suguru
Published: July 2009

The dynamics of the biped locomotion system with many degrees of freedom are analyzed from a control theoretic point of view. By the use of the singular perturbation technique, it is shown that biped locomotion can be divided into two modes with respective time scales, the fast mode and the slow mode. Based on this fact, a control system for dynamical biped locomotion is constructed. The effectiveness of the proposed control algorithm is verified using computer simulation.
Stabilizing Feedback Controls for Nonlinear Hamiltonian Systems and Nonconservative Bilinear Systems in Elasticity
Authors: Singh S. N.
Published: July 2009

Using the invariance principle of LaSalle [1], sufficient conditions for the existence of linear and nonlinear control laws for local and global asymptotic stability of nonlinear Hamiltonian systems are derived. An instability theorem is also presented which identifies the control laws from the given class which cannot achieve asymptotic stability. Some of the stability results are based on certain results for the univalence of nonlinear maps. A similar approach for the stabilization of bilinear systems which include nonconservative systems in elasticity is used and a necessary and sufficient condition for stabilization is obtained. An application to attitude control of a gyrostat Satellite is presented.
A Study on Parameter Determination Method of Large-Scale and Complex Dynamic Systems With Judgment Functions (No. 2)—Applications
Authors: Furukawa Osamu , Hiroyasu Hiroyuki , Iida Satoshi
Published: July 2009

This paper deals with the parameter satisfaction problems of gas exchanging system, which are important from a standpoint of quality design. These problems have been difficult to solve, because their mathematical models are described by large-scale and complex dynamic system equations with many judgment functions. The report No. I [1] has already proposed the method to solve the parameter satisfaction problems of such systems. This method is one which sequentially exchanges the original mathematical model to the analyzable approximate model by means of selection of attributes with analysis-charts and statistical identification method with jump condition extended and which improves parameters simultaneously. In this paper, this method is applied to the above problems and a parameter improvement system which can improve many parameters efficiently without enormous calculations of partial derivatives is constructed. By the numerical calculations, satisfactory parameters could be obtained and it is shown that this method can give the solutions of the above problems. Moreover, its effectiveness for the fundamental and unsettled problems of such large-scale and complex systems in the field of mechanical engineering is demonstrated.
Freight Car Lateral Dynamics—An Asymptotic Sketch
Authors: Whitman Alan M. , Khaskia Abdul-Rahman M.
Published: July 2009

We analyze a model of a freight car using asymptotic methods and obtain a formula for the critical speed that is valid over a wide range of warp stiffnesses. We also discuss corrections to this formula that are engendered by the other parameters that influence the motion. The results of the analysis are compared with numerical solutions of the model in order to assess their accuracy.
Effects of Thermal Damping on the Dynamic Response of a Hydraulic Motor-Accumulator System
Authors: Pourmovahed A. , Otis D. R.
Published: July 2009

A hydraulic accumulator is often modeled as a gas spring following a polytropic process, but this fails to properly account for the dissipative effects of heat transfer which produce damping and phase shift in the dynamic behavior. A thermal time constant can properly characterize the heat transfer between the charge gas and the accumulator walls, and it is shown that for the linearized case the accumulator becomes equivalent to the Anelastic Model. The transfer function for the accumulator is derived, and the mathematical solution is presented for a hydraulic accumulator coupled to the inlet of a hydraulic motor where the load force is subject to a small, sinusoidal variation with time. Experimental data are presented to show that the accumulator can be accurately modeled using a thermal time constant, and the Anelastic Model would adequately describe the accumulator for the case of small perturbations.
Experiments in Balance With a 2D One-Legged Hopping Machine
Authors: Raibert M. H. , Brown H. B.
Published: July 2009

The ability to balance is important to the mobility obtained by legged creatures found in nature, and may someday lead to versatile legged vehicles. In order to study the role of balance in legged locomotion and to develop appropriate control strategies, a 2D hopping machine was constructed for experimentation. The machine has one leg on which it hops and runs, making balance a prime consideration. Control of the machine’s locomotion was decomposed into three separate parts: a vertical height control part, a horizontal velocity part, and an angular attitude control part. Experiments showed that the three part control scheme, while very simple to implement, was powerful enough to permit the machine to hop in place, to run at a desired rate, to translate from place to place, and to leap over obstacles. Results from modeling and computer simulation of a similar one-legged device are described by Raibert [10].