bluuebunny/crossref_metadata_2025 huggingface dataset:
On-Line Optimization Using Dual Decomposition and a Quasilinear Subsystem Expansion
Authors: Perry P. F.
Published: July 2009

The problem of on-line optimal control of large scale interconnected nonlinear dynamic systems is considered using duality. A well-known goal coordination algorithm is used involving two levels of computation: at level 1 a decomposed Lagrangian function is minimized with respect to its subsystem states and controls for a given multiplier value obtained by maximizing the dual with respect to the coordinating constraints at level 2. The level 1 computation is carried out for nonlinear problems using a quasilinear expansion from which the resulting two point boundary value problems are solved using a procedure due to Pereyra. The level 2 computation is carried out using conjugate gradients. A numerical example is given and some potential application areas in process and factory automation are mentioned.
Least Squares Adaptive Control for Trajectory Following Robots
Authors: deSilva C. W. , Van Winssen J.
Published: July 2009

A control scheme is presented for trajectory following with robotic manipulators. The method employs a feedforward torque for gross compensation and adaptive feedback gain scheduling for correcting deviations from the desired trajectory. The adaptive controller eliminates trajectory errors in the least squares sense without using online identification or a reference model. The control scheme takes into account dynamic nonlinearities (e.g., coriolis and centrifugal accelerations and payload changes), geometric nonlinearities (e.g., nonlinear coordinate expressions for large excursions) and physical nonlinearities (e.g., nonlinear damping) as well as dynamic coupling present in a manipulator. The method can accommodate real-time changes in the desired trajectory. In practice, a recursive algorithm would be needed to accomplish this. Computer simulations are given to demonstrate the feasibility of the control scheme.
Nonlinear Regulators for a Class of Decomposable Systems
Authors: Kimbrough S.
Published: July 2009

This paper presents nonlinear regulators for a large class of systems that includes many linear systems, bilinear systems, and variable structure systems. Membership in this class requires that the dynamic equations of a system decompose into a set of stable equations and into a set of equations which are nulled by some feasible control value. When the stable set of equations represents a linear system and the remaining set of equations is linear in the control variables (with other variables fixed), the resulting regulators become attractive alternatives to linear regulators. They have time invariant forms suitable for real-time control, have the capability to handle complicated constraints, and have control properties beyond the range of linear regulators. The procedure followed is to obtain a Lyapunov function for the stable set of equations, which is then used to assure closed loop stability. Sufficient conditions for maintaining Lyapunov stability are treated as constraints in optimizations that yield the control policies. These constraints can always be satisfied because it is assumed that some feasible control nulls the remaining set of equations. The benefits of this procedure are that stability can be obtained by working with a smaller more manageable set of equations than the full system equations and control policies can be obtained from readily solvable optimizations. Although the resulting nonlinear regulators are suboptimal their performance can often be bounded by the performance of an optimal linear regulator.
An Approach to Multivariable Control of Manipulators
Authors: Seraji H.
Published: July 2009

The paper presents simple schemes for multivariable control of multiple-joint robot manipulators in joint and Cartesian coordinates. The joint control scheme consists of two independent multivariable feedforward and feedback controllers. The feedforward controller is the minimal inverse of the linearized model of robot dynamics and contains only proportional-double-derivative (PD2) terms—implying feedforward from the desired position, velocity and acceleration. This controller ensures that the manipulator joint angles track any reference trajectories. The feedback controller is of proportional-integral-derivative (PID) type and is designed to achieve pole placement. This controller reduces any initial tracking error to zero as desired and also ensures that robust steady-state tracking of step-plus-exponential trajectories is achieved by the joint angles. Simple and explicit expressions for computation of the feedforward and feedback gains are obtained based on the linearized model of robot dynamics. This leads to computationally efficient schemes for either on-line gain computation or off-line gain scheduling to account for variations in the linearized robot model due to changes in the operating point. The joint control scheme is extended to direct control of the end-effector motion in Cartesian space. Simulation results are given for illustration.
Tool Positioning for Noncircular Cutting With Lathe
Authors: Tomizuka M. , Chen M. S. , Renn S. , Tsao T. C.
Published: July 2009

This paper presents the design and implementation of a digital controller for a lathe to machine workpieces with noncircular cross sections. Noncircular cutting is accomplished by controlling the radial tool position in the direction normal to the surface of workpiece. A discrete time model for the tool carriage in the radial direction is obtained by a least squares method applied to input and output data. The model is used for designing digital feedback and feedforward controllers. The zero phase error tracking control algorithm is applied as a feedforward control law for positioning of the tool along desired time varying signals. The effectiveness of the proposed controller is demonstrated by experiment and simulation.
On the New Equations for the Lateral Dynamics of a Rail-Tie Structure
Authors: Kerr A. D. , El-Sibaie M. A.
Published: July 2009

The accuracy of the new equations for the rail-tie structure, derived by Kerr and Zarembski and recently generalized for dynamic problems by Kerr and Accorsi, is studied. This is done by comparing the natural frequencies based on the new equations with those calculated using a finite element method for a range of fastener stiffness values and a variety of rail spacings. The comparison revealed very close agreement. The findings confirm the suitability of the new equations for dynamic analyses of cross-tie tracks in the lateral plane.
Motion Control Analysis of a Mobile Robot
Authors: Borenstein J. , Koren Y.
Published: July 2009

A computer-controlled vehicle that is part of a mobile nursing robot system is described. The vehicle applies a motion control strategy that attempts to avoid slippage and minimize position errors. A cross-coupling control algorithm that guarantees a zero steady-state orientation error (assuming no slippage) is proposed and a stability analysis of the control system is presented. Results of experiments performed on a prototype vehicle verify the theoretical analysis.
Optimal Trajectory Generation for Robotic Manipulators Using Dynamic Programming
Authors: Singh S. , Leu M. C.
Published: July 2009

The problem of optimal control of robotic manipulators is dealt with in two stages: (1) optimal trajectory planning, which is performed off-line and results in the prescription of the position and velocity of each link as a function of time along a “given” path and (2) on-line trajectory tracking, during which the manipulator is guided along the planned trajectory using a feedback control algorithm. In order to obtain a general trajectory planning algorithm which could account for various constraints and performance indices, the technique of dynamic programming is adopted. It is shown that for a given path, this problem is reduced to a search over the velocity of one moving manipulator link. The design of the algorithm for optimal trajectory planning and the relevant computational issues are discussed. Simulations are performed to test the effectiveness of this method. The use of this algorithm in conjunction with an on-line controller is also presented.
A New Approach to Kinematic Control of Robot Manipulators
Authors: Goldenberg A. A. , Apkarian J. A. , Smith H. W.
Published: July 2009

A new approach for solving the inverse kinematics problem iteratively is presented. The solution is based on the recursive estimation of a kinematics operator which maps the task space coordinates into joint coordinates. The recursive estimation is based on least square approximation. For controlling the robot, the solution (Joint coordinates) must be compensated to achieve an arbitrarily small error (in least square sense) of the desired task space coordinates. The compensation is provided by closed loop feedback of task space coordinates using an optimal control approach.
Robust Sliding-Mode Control of a Nonlinear Process With Uncertainty and Delay
Authors: Young G. E. , Rao S.
Published: July 2009

A nonlinear variable structure control strategy is combined with the reaction invariant to control pH in a mixing tank with process delay. A nonlinear predictor is utilized to estimate the actual pH from its measured value. System response is significantly improved by overlaying a variable structure on the controller gains. Uncertainty in the process delay, titration curve, and influent disturbance is incorporated into the controller design. Simulation studies show that Robust controller design is obtained by incorporating a procedure based on the binary classification of the system response to produce system behavior which is insensitive to the given system parameter uncertainty. This procedure provides a practical design of a sliding-mode controller regulating a system with significant process delay where the system state is not directly available.
Adaptive Robust Model-Following Control and Application to Robot Manipulators
Authors: Chen Y. H.
Published: July 2009

The model-following control problem for nonlinear uncertain dynamical systems is considered. Based only on the knowledge of functional properties relating to the bound of the time-varying uncertainty, a class of adaptive feedback controls is developed which, under some realistic assumptions, guarantees the error between the uncertain dynamical system and the model tends to be zero. Application to robotic manipulators is made.
An Optimal Control Method for Passage of a Flexible Rotor Through Resonances
Authors: Viderman Z. , Porat I.
Published: July 2009

This paper deals, by means of modal analysis, with the effects of control forces on passage through resonances of a flexible rotor. Several control methods are evaluated, and the necessary number of dampers and their optimal location are determined. A fundamental interpretation is offered for the problem as a whole.
The Design of Open-Loop Manipulator Arms With Decoupled and Configuration-Invariant Inertia Tensors
Authors: Youcef-Toumi Kamal , Asada Haruhiko
Published: July 2009

A manipulator design theory for reduced dynamic complexity is presented. The kinematic structure and mass distribution of a manipulator arm are designed so that the inertia matrix in the equation of motion becomes diagonal and/or invariant for an arbitrary arm configuration. For the decoupled and invariant inertia matrix, the system can be treated as a linear, single-input, single-output system with constant parameters. Consequently, control of the manipulator arm is simplified, and more importantly, the reduced dynamic complexity permits improved control performance. First, the problem of designing such an arm with a decoupled and/or configuration-invariant inertia matrix is defined. The inertia matrix is then analyzed in relation to the kinematic structure and mass properties of the arm links. Necessary conditions for a decoupled and/or configuration-invariant manipulator inertia matrix are then obtained. Using the necessary conditions, the kinematic structure and mass properties are found which reduce the inertia matrix to a constant diagonal form. Possible arm designs for decoupled and/or invariant inertia matrices are then determined for 2 and 3 degree-of-freedom manipulators.
Discrete Time Model Reference Adaptive Control of an Industrial Manipulator’s Waist Joint
Authors: Kuo C.-Y. , Worger W.
Published: July 2009

The current control systems adopted by most industrial manipulators are “open loop” designs based only upon kinematic consideration. Their servo gains are fixed and there is no flexibility of updating them. It is desirable, therefore, to have a robot control system that adapts to its payload and manipulator configuration in order to maintain optimal dynamic performance throughout the robot workspace, and regardless of the payload. This paper implements and evaluates the discrete time model reference adaptive control (MRAC) algorithm of robot control proposed by Horowitz and Tomizuka to a PUMA 560 industrial robot. Its original controller was overridden and the individual joint axes are controlled by a separate computer. This study shows the adaptive controller can maintain fast, consistent response regardless of the arm configuration.
Control of a Flexible Robot Arm: Experimental and Theoretical Results
Authors: Chalhoub N. G. , Ulsoy A. G.
Published: July 2009

The operation of high precision robots is severely limited by. their manipulator dynamic deflection, which persists for a period of time after a move is completed. These unwanted vibrations deteriorate the end effector positional accuracy and reduce significantly the robot arm production rate. A “rigid and flexible motion controller” is derived to introduce additional damping into the flexible motion. This is done by using additional sensors to measure the compliant link vibrations and feed them back to the controller. The existing actuators at the robot joints are used (i.e., no additional actuators are introduced). The performance of the controller is tested on a dynamic model, developed in previous work, for a spherical coordinate robot arm whose last link only is considered to be flexible. The simulation results show a significant reduction in the vibratory motion. The important issue of control and observation spillover is examined and found to present no significant practical problems. Partial evaluation of this approach is performed experimentally by testing two controllers, a “rigid body controller” and a “rigid and flexible motion controller,” on a single joint of a spherical coordinate, laboratory robot arm. The experimental results show a significant reduction in the end effector dynamic deflection; thus partially validating the results of the digital simulation studies.
Exploiting Bond Graph Causality in Physical System Models
Authors: Rosenberg R. C.
Published: July 2009

Causality as a concept and a tool associated with bond graphs has seen use for more than twenty years. Our principal purpose in this paper is to bring together several different views and applications of causality in order to suggest how valuable it can be in understanding the dynamic structure of models. The topics considered include causality assignment, both traditional and nontraditional, and state equations; design assessment of models based on direct interpretation; and junction structure properties. The topics are illustrated by examples. Some opportunities for additional research into causality properties and applications are suggested.
Wheel Wear Predictions for Tangent Track Running
Authors: Fries R. H. , Da´vila C. G.
Published: July 2009

Wear of wheels and rails is a problem of substantial magnitude for railways throughout the world. Efforts to control wear by using new wheels profiled to match worn wheels have met with a measure of success. Purely empirical approaches to this problem require years of effort before results can be assessed. This paper describes a computational method for predicting worn profiles. The method is applied here to freight cars running on tangent track, and it includes the capability to handle both stable and hunting running. The method has been evaluated with four different wear models, and it was found that the predicted worn wheel profiles are relatively insensitive to the selection of wear model. Results include predictions from AAR and CNA wheels running on new rail, and from a simulated unit-train operation.
Whistling Instability in Idling Circular Saws
Authors: Mote C. D. , Leu M. C.
Published: July 2009

Whistling is a self-excited transverse instability that produces intense noise at a resonant frequency of a circular saw. Experiments were undertaken to examine the noise source dependence upon tooth shape, tooth number, rotation speed and the surrounding air pressure. The source model supported by the data is a self excited fluid-structure instability possibly with a wake oscillation sustained or enhanced by the blade motion.
Rufus Oldenburger Award: Henry M. Paynter
Authors: Zwiep Donald N.
Published: July 2009

“In recognition of his creative accomplishments in all aspects of dynamic systems theory and practice, his inspiring example to students and colleagues, and his supreme enthusiasm. His accomplishments include, but are hardly limited to, innovations in fluid transmission line and fluid transient theory, seminal contributions to analog, digital and hybrid simulation methodology, and development of an integrated notational and computational framework for energetic systems (bond graphs).”
On-Line Computational Scheme for Mechanical Manipulators
Authors: Luh J. Y. S. , Walker M. W. , Paul R. P. C.
Published: July 2009

Industrial robots are mechanical manipulators whose dynamic characteristics are highly nonlinear. To control a manipulator which carries a variable or unknown load and moves along a planned path, it is required to compute the forces and torques needed to drive all its joints accurately and frequently at an adequate sampling frequency (no less than 60 Hz for the arm considered). This paper presents a new approach of computation based on the method of Newton-Euler formulation which is independent of the type of manipulator-configuration. This method involves the successive transformation of velocities and accelerations from the base of the manipulator out to the gripper, link by link, using the relationships of moving coordinate systems. Forces are then transformed back from the gripper to the base to obtain the joint torques. Theoretically the mathematical model is “exact”. A program has been written in floating point assembly language which has an average execution time of 4.5 milliseconds on a PDP 11/45 computer for a Stanford manipulator. This allows an on-line computation within control systems with a sampling frequency no lower than 60 Hz. A further advantage of using this method is that the amount of computation increases linearly with the number of links whereas the conventional method based on Lagrangian formulation increases as the quartic of the number of links.
Model-Reference Longitudinal Control for Automated Vehicle Systems
Authors: Caudill R. J. , Blasnik S. L.
Published: July 2009

The problem of designing longitudinal control systems which provide acceleration and jerk limited response for automated vehicle systems is examined. Non-dimensional models of vehicles propelled by d-c traction motors are used to evaluate the feasibility of the model-reference control concept. Analytical and computer simulation techniques are used to evaluate performance and assure critical string behavioral characteristics - asymptotic string stability and fixed end-point speed transition region (proper curve negotiation).
Coupled Lateral-Vertical Dynamics of Rubber-Tired Automated Guideway Transit Vehicles With Random Guideway Inputs
Authors: Kwak Y. K. , Smith C. C.
Published: July 2009

A method is presented which permits the simulation of the coupled lateral-vertical rigid body vibration response of a rubber-tired automated guideway transit (AGT) vehicle subject to guideway random irregularities. A coupled lateral-vertical dynamic model is developed. The general motions are expressed by Euler angles and inertial displacements. Basic vehicle dynamic modes are determined. A predicted lateral acceleration spectrum of the linearized model using guideway surface profile models for inputs are compared with the measured lateral acceleration spectra and found to agree reasonably well in the lower frequency (below about 7 Hz) range. Good agreement was found to exist between the predicted and measured root mean square (rms) accelerations for a wider range of frequencies.
Bond Graphs for Distributed System Models Admitting Mixed Causal Inputs
Authors: Margolis D. L.
Published: July 2009

Bond graphs are used for finite mode representations of distributed system dynamics. As long as all inputs to the system are “efforts” in a causal sense, then no formulation problems exist. However, if some of the system inputs are causal “flows”, then differential causality will exist and extremely tedious, often impossible, algebraic loops must be solved to formulate system equations. A procedure is developed which avoids these algebraic problems by including additional modal compliance in the system model without its associated modal inertia. The result of this approach is a finite mode distributed system model, devoid of artificially induced high frequencies, extremely accurate in a chosen frequency range, and capable of interacting with other distributed system models. The procedure is demonstrated through example.
High Priority Research Relevant to Energy Issues in the Field of Process and Systems Dynamics and Control
Authors: Rabins M. J. , Edgar T. F. , Richardson H. H. , Zaborszky J.
Published: July 2009

This paper summarizes a set of high priority basic engineering research needs in the field of Process and Systems Dynamics and Control which are important to the development of future energy technologies. These needs have been defined and recommended to the U. S. Department of Energy (DOE) under the direction and oversight of the American Automatic Control Council representing the major professional societies having expertise in the field. Ten generic research areas have been defined which are grouped within four major recommended fields of basic engineering research: on-line optimization and control, systems methodology, measurement methodology and instrumentation, and modeling. Research in each of these fields has the potential for broad energy impact in transportation, processing, energy conversion and delivery, manufacturing, environmental aspects and other applications which consume significant amounts of energy. It is estimated that the recommended research could result in savings of total energy use of 1–10 percent depending on the application, which at current prices could range from $5 to $50 billion per year, based on research funding of $20 to $30 million per year. The results and recommendations summarized in this paper are based on the report entitled, “Basic Research in Engineering: Process and Systems Dynamics and Control” [1].
Design of Digital Feedforward/Preview Controllers for Processes With Predetermined Feedback Controllers
Authors: Tomizuka Masayoshi , Fung D. H.
Published: July 2009

This paper deals with the design of digital feedforward/preview (F/P) controllers for multi-input, multi-output processes with predetermined feedback controllers. The feedback controller is assumed to include an integral action which operates upon the error between setpoint and process output. The feedforward/preview controller is a weighted sum of previewed values of future disturbances. Formula for the F/P control gains are derived using a parameter optimization technique to minimize a quadratic cost criterion. Simulation examples are included to show some of the consequences of the developed design method.
On the Periodic Response of Cam Mechanism With Flexible Follower and Camshaft
Authors: Midha A. , Turcic D. A.
Published: July 2009

Researchers in recent years have shown a great deal of interest in the study of the dynamic response of cam-follower systems, with one or more of its components treated as being elastic. Within the assumption of a lineaar analysis, and limited to stable regions, a single degree-of-freedom linear second order differential equation of motion is developed for a cam mechanism consisting of elastic follower and camshaft. This development is consistent, as are some simplifying assumptions, with the works of current authors. The governing equation is shown to possess time-dependent periodic coefficients, for a constant imput angular velocity. Conventionally, the rise portion of the cam motion cycle has been treated as the source of excitation, and the transient follower-motion computed during the excitation (rise) as well as the subsequent dwell periods. The one basic assumption in these works, however, has been that the residual vibration is damped out during the dwell period and does not carry over to the next motion cycle. In this paper, the authors forego this assumption and present a method for not only incorporating the excitation effects due to the return stroke, but also for obtaining the steady-state response of the follower. Some illustrative examples are presented, and even though no comprehensive set of cam-profile types are examined, some basic conclusions are reached using a representative cycloidal cam profile.
Rail Vehicle Active Suspensions for Lateral Ride and Stability Improvement
Authors: Celniker G. W. , Hedrick J. K.
Published: July 2009

The potential performance benefits of simple, low power active elements in the lateral secondary, between the truck and carbody is investigated analytically by parametric studies utilizing a fifteen degree of freedom lateral dynamic model subject to alignment and cross-level inputs. It is shown that significant improvements in ride quality can be obtained at current operating speeds by using less than 3 kw per truck by sensing lateral carbody accelerations and utilizing lateral force actuators between the truck and carbody. It is also shown that in order to improve the truck critical speed and/or to improve the ride quality at very high speeds requires control of the truck kinematic mode. This can be achieved, at the expense of increased power requirements, by sensing absolute truck lateral and yaw velocities and utilizing combined lateral force actuators to exert a yaw moment on the truck. It is concluded that significant ride quality improvements can be achieved by low power, small bandwidth actuators while stabilty improvements requires increased power and larger bandwidth systems.
Routh Approximations for Reducing Order of Discrete Systems
Authors: Hwang Chyi , Shin Yen-Ping
Published: July 2009

Routh approximation method is extended to the simplification of z-transfer functions. The procedure includes (1) transformation of the z-transfer function into the w-domain, (2) γ-δ expansion of the w-transfer function, (3) truncation the higher-order terms in the γ-δ expansions, and (4) transformation of the reduced w-transfer function into the z-domain. The reduced model is always stable if the original high-order system is stable. A numerical example is inclinded to illustrate the procedure.
The Inverse Kinematic Problem for Anthropomorphic Manipulator Arms
Authors: Benati Mauro , Morasso Pietro , Tagliasco Vincenzo
Published: July 2009

The inverse kinematic problem for manipulator arms consists of computing the time course of the joint free variables, which correspond to a desired time course of the position/orientation of the hand in space. This problem involves the solution of complicated trigonometric equations and furthermore, for anthropomorphic manipulator arms (which have at least seven degrees of freedom), the problem is underdetermined, requiring therefore to solve an associated optimization task. The proposed approach is recursive, partly analytical and partly numerical. From a geometrical model of the arm, based on rotation matrices and Rodrigues vectors, we derive two algorithms: the former computes a sequence of arm configurations (the output variables) from a given sequence of hand positions/orientations (the input variables) and the latter adjusts the updated configurations according to a quadratic optimization criterion.
On-Line Algorithms for Initial State Identification in Linear Systems
Authors: Sehitoglu H.
Published: July 2009

This paper presents on-line algorithms to identify the unknown initial state of a linear system. It is shown that estimation of an initial state vector can be treated as a parameter identification problem. The algorithms are developed by using the equation error identification technique in connection with the Lyapunov design approach. An example problem is considered to illustrate the concepts discussed in the paper.
A Steering Control System to Minimize Propulsion Losses of High-Speed Containerships—Part I: System Dynamics
Authors: Reid R. E. , Moore J. W.
Published: July 2009

The problem of steering control of high-speed containerships to minimize propulsion losses is addressed. The approach involves time domain modeling and simulation. A dynamic model of a containership and steering system in a seaway is constructed. Performance criteria for added resistance associated with yawing and steering are discussed. Losses resulting from yawing of the uncontrolled ship in heavy weather are shown by simulation to be significant. The results presented form a basis for design of a controller to minimize steering related losses.
Asynchronous Interactive Control Systems
Authors: Vusˇkovic´ M. I. , Heer E.
Published: July 2009

A class of interactive control systems is derived by generalizing interactive manipulator control systems. The general structural properties of such systems are discussed and an appropriate general software implementation is proposed. This is based on the fact that tasks of interactive control systems can be represented as a network of a finite set of actions which have specific operational characteristics and specific resource requirements, and which are of limited duration. This has enabled the decomposition of the overall control algorithm into a set of subalgorithms, called subcontrollers, which can operate simultaneously and asynchronously. Coordinate transformations of sensor feedback data and actuator set-points have enabled the further simplification of the subcontrollers and have reduced their conflicting resource requirements. The modules of the decomposed control system are implemented as parallel processes with disjoint memory space communicating only by I/O. The synchronization mechanisms for dynamic resource allocation among subcontrollers and other synchronizaton mechanisms are also discussed in this paper. Such a software organization is suitable for the general form of multiprocessing using computer networks with distributed storage.
Quasi-Static Assembly of Compliantly Supported Rigid Parts
Authors: Whitney D. E.
Published: July 2009

Geometric and force equilibrium conditions for successfully mating rigid parts are presented. The action of the Remote Center Compliance is explained. Guidelines for choosing RCC parameters are presented. Models of insertion force behavior are verified by experimental data.
The Determination of Modal Damping Ratios From Maximum Entropy Spectral Estimates
Authors: Campbell R. B. , Vandiver J. K.
Published: July 2009

This paper focusses on the estimation of natural frequencies and modal damping ratios from measured response spectra, with particular emphasis on the dynamic response of offshore structures to wind and wave excitation. At present, estimates of natural frequencies and damping ratios are computed from the location and half-power bandwidths of resonant peaks in a structure’s ambient response power spectrum. While reliable natural frequency estimates are typically obtained in this manner, half-power bandwidth damping estimates are shown to be highly sensitive to the method employed in estimating the response spectrum. The lack of confidence bounds on natural frequency and damping estimates further restricts the utility of the estimates. An alternative method is developed based on a powerful method of spectral estimation known as the Maximum Entropy Method (MEM). The resulting technique yields estimates of natural frequencies and modal damping ratios as well as approximate statistics on the reliability of the estimates. Performance of this new method is explored through extensive Monte Carlo simulation of one and two degree-of-freedom systems. Conventional estimates are also simulated for comparison with the MEM parameter estimator. The use of the MEM parameter estimator is further illustrated with ambient response data from Shell Oil’s South Pass 62C platform. The MEM parameter estimates show excellent agreement with natural frequency and damping estimates obtained during recent tests conducted using forced excitation.
Dynamic Modeling of a Wheelchair on a Slope
Authors: Shung J. B. , Stout G. , Tomizuka M. , Auslander D. M.
Published: July 2009

This paper describes a computer model of a wheelchair and its motor control circuitry. The model simulates the wheelchair’s motion in driving on a sloping surface, and is intended to facilitate the design of wheel velocity feedback controller. Experimental data are presented to partially validate the model.
On The Lateral Stability of a Flexible Truck
Authors: Whitman A. M.
Published: July 2009

Analytic formulae for the critical speed and frequency of an interconnected pair of wheelsets based on an asymptotic expansion in a truck geometric parameter are derived. No restriction is placed on the values of either the shear or bending stiffness; consequently, the entire structure of the stability surface is obtained. The surface is a symmetric function of the two dimensionless stiffnesses and it depends predominantly on their series combination. Expressions are obtained for the local and global extrema and their locations. The frequency varies monotonically from the wheelset kinematic frequency to the rigid truck frequency as a function of stiffness. The results are compared with numerical solutions and found to be accurate in the region of physically obtainable values of the expansion parameter.
Alternative Bond Graph Causal Patterns and Equation Formulations for Dynamic Systems
Authors: Karnopp Dean
Published: July 2009

Given mathematical models of components of a system, the equations for the system can be formulated in a number of distinct ways. Bond graphs provide a convenient explicit way to study the interactions among component models and the system equation formulations which follow from the various ways in which input-output causality can be assigned. Three means of causality assignment are compared: an all-integral method, an all derivative method, and a Lagrange-equation procedure. Some interesting differences among the procedures occur when fields (dependent state variables) or nonlinear junction structures (geometric nonlinearities) are present in the system model.
A Study on Parameter Determination Method of Large-Scale and Complex Dynamic Systems With Judgment Functions (No. 1)—Theory
Authors: Furukawa Osamu , Ikeshoji Hideomi , Iida Satoshi
Published: July 2009

In the design of large-scale and complex mechanical systems, determination of design parameters is a very difficult problem. This study deals with parameter satisfaction problems of large-scale, complex, and dynamic systems with judgment functions. In order to solve these problems, a new method is proposed which sequentially exchanges the original mathematical model to an analyzable approximate model by means of the identification method and which improves a lot of parameters simultaneously. First, criteria of selection of attributes to build up approximate model are clarified. Moreover, as tools for selection of attributes, two analysis charts are proposed which express dynamic relationships among the attributes. Second, a general condition to determine the structure of approximate models and a statistical method to linearize the original model with judgment functions are derived. Finally, a combinatorial method of statistical identification and parameter optimization methods are proposed. By this method, some shortcomings of sensitivity analysis, decomposition technique (enormous calculations of partial derivatives) and statistical methods such as Monte Carlo method (bad convergency of solutions) can be avoided. As a result of this, it becomes possible to search satisfactory parameters efficiently.
Dynamic Scaling of Manipulator Trajectories
Authors: Hollerbach J. M.
Published: July 2009

A fundamental time-scaling property of manipulator dynamics has been identified that allows modification of movement speed without complete dynamics recalculation. By exploiting this property, it can be determined whether a planned trajectory is dynamically realizable given actuator torque limits, and if not, how to modify the trajectory to bring it within dynamic and actuating constraints.
Perturbation Analysis of Optimal Integral Controls
Authors: Slater G. L.
Published: July 2009

The application of linear optimal control to the design of systems with integral control action on specified outputs is considered. Using integral terms in a quadratic performance index, an asymptotic analysis is used to determine the effect of variable quadratic weights on the eigenvalues and eigenvectors of the closed loop system. It is shown that for small integral terms the placement of integrator poles and gain calculation can be effectively decoupled from placement of the primary system eigenvalues. This technique is applied to the design of integral controls for a STOL aircraft outer loop guidance system.
Dynamic Turbocharged Diesel Engine Simulator for Electronic Control System Development
Authors: Watson N.
Published: July 2009

A nonlinear dynamic simulation of a turbocharged diesel engine is presented. The model is designed to be used as an engine simulator to aid development of advanced microelectronic control systems of varying degrees of complexity and performance. The objective is to establish the potential benefit of quite different control system concepts in advance of hardware being constructed and tested on an engine. The detail of the model is governed by the desire to accurately predict fuel economy of new engine designs currently on the drawing board, without empirical input, and respond correctly to changing ambient conditions, design alterations etc. Thus the model treats cylinders and manifolds as thermodynamic control volumes, solving energy and mass conservation equations with subroutines for combustion, heat transfer, turbocharger, dynamic aspects etc. In-cylinder calculations are performed in small engine crank-angle steps so that the correct ignition crank angle is predicted as well as the subsequent fuel burning rate. This enables parameters such as cylinder pressure and diffusion burning factor (which correlates with exhaust smoke) to be predicted. The conflict between accuracy and computer run time and cost is addressed, and it is shown how the run time of a previous model (see SAE 770123) has been reduced by an order of magnitude. The accuracy of the model is illustrated by comparing measured and predicted performance over the complete engine speed and load range under steady conditions and engine response to “full throttle” acceleration and full-load application. The model is then used to show the influence of design parameters such as injection timing and turbocharger characteristics as well as external influence such as fuel cetane number and ambient conditions on steady speed and dynamic performance.
On a Magnetic Damper Consisting of a Circular Magnetic Flux and a Conductor of Arbitrary Shape. Part II: Applications and Numerical Results
Authors: Nagaya Kosuke
Published: July 2009

A method of numerical calculation for obtaining the damping coefficients and potential fields has been presented for magnetic dampers by utilizing the theoretical results given by the authors in a companion paper (Part I). The study developed in this paper is concerned with dampers consisting of the following conductors and magnetic fluxes: (a) a rectangular conductor and an eccentric circular flux, (b) a circular conductor and an eccentric circular flux, and (c) polygonal conductors of various shapes and a concentric circular flux. Numerical results for the damping coefficients, and potential lines of the magnetic fields have been obtained for these dampers. The results obtained are compared with those of the typical case of the conductor with a concentric circular flux.
Load Torque Effects on the Critical Speeds of a Continuous Rotor
Authors: Cohen R. , Porat I.
Published: July 2009

The paper deals with the influence of the load torque on the critical velocities of a shaft mounted on short bearings. While in most works on this subject the load torque is taken as axial, it is shown here that, provided the external torque does not change its initial direction as the shaft is deformed and is applied through an ideal spherical coupling—the assumption of a semitangential mode is the correct one. Revised values of the critical torques and velocities are calculated accordingly and compared to those based on the conventional assumption.
An Improved Method of Dynamic Coupling in Structural Analysis and Its Applications
Authors: Inamura Toyoshiro , Suzuki Hiromasa , Sata Toshio
Published: July 2009

An improved method of dynamic coupling is developed for use in an interactive structural analysis system proposed by the authors. The method is used to couple the values of the lowest few modes of the dynamic characteristics of structures at a high speed. Additional techniques are proposed to confine computation to those points necessary for evaluation and to couple the values under the condition that the nodal points to be connected have different coordinates from each other. Some examples of the analyses are illustrated to show the efficiency of the proposed methods.
Photofluidic Interface
Authors: Gurney J. O.
Published: July 2009

A device that transduces optical control signals to pneumatic control pressures was assembled and tested. This photofluidic interface uses no electronic components and requires no electrical power. The interface employs the photoacoustic effect and fluidic signal processing techniques. The pressure output from the interface can be controlled by modulating the input optical signal in any one of four different ways (amplitude modulation, frequency modulation, pulse width modulation, and gate width modulation). Results of performance tests are reported. There is also a discussion of the physical parameters involved in the conversion of optical signals to fluidic signals.
Statistical Analysis of the AR Type Ship’s Autopilot System
Authors: Ohtsu Kohei , Kitagawa Genshiro
Published: July 2009

We statistically analyze the actual ship motion steered by the AR autopilot system developed by the authors in 1977. The analysis is based on a multivariate AR modeling of time series observed at the experiments. The course keeping qualities and the control laws are compared with the conventional PID autopilot system. Various possible extensions of the AR autopilot to adaptive ones are also discussed.
Modelling and Adaptive Control of a Mechanical Manipulator
Authors: Anex R. P. , Hubbard Mont
Published: July 2009

This paper implements and evaluates the adaptive control algorithm recently proposed by Horowitz and Tomizuka. A dynamic model of the Rhino XR-2 manipulator arm is developed using bond graph techniques. The manipulator and the control algorithm are simulated. The manipulator is then adaptively controlled. The study offers valuable insight into the practical problems associated with actual implementation of adaptive control algorithms and fully describes one of the few case studies of adaptive control in a working physical system. The physical problems directly addressed are disturbances due to Coulomb friction, gravitational loading, and actuator saturation.
Analysis of a Semi-Levered Suspension Landing Gear With Some Parametric Study
Authors: Jayarami Reddy P. , Nagaraj V. T. , Ramamurti V.
Published: July 2009

A set of nonlinear differential equations describing the response of a semilevered suspension type of landing gear with a single stage oleo-pneumatic shock strut is derived. This includes the kinematics of the articulation of the gear, oil compressibility effect, wheel spin-up as a function of slip ratio, and the hydraulic, pneumatic, and friction forces of the shock strut. A parametric study on a gear of a helicopter has been conducted and the effect of variations in the main orifice diameter, coefficient of discharge of main orifice, initial air volume and pressure, polytropic exponent for air compression process, coefficients of friction at lower and upper bearings and the horizontal velocity of the aircraft during landing on the behavior of the landing gear has been studied.
Analysis and Design of a Direct-Drive Arm With a Five-Bar-Link Parallel Drive Mechanism
Authors: Asada Haruhiko , Youcef-Toumi Kamal
Published: July 2009

The direct-drive arm that has no gears between motors and their loads have several important advantages including no backlash, small friction, and high mechanical stiffness. The arm mechanism, however, becomes extremely massive, when each motor is directly attached to its joint along a serial linkage mechanism. The complicated dynamics resulting from varying inertia, interactions, and nonlinearities, is also more prominent than that of a robot with gears. This paper describes a lightweight arm mechanism with invariant and decoupled inertia characteristics. Instead of having motors at serial joints, a parallel drive mechanism with a closed-loop five bar linkage is utilized. The dynamic behavior of this mechanism is analyzed and the condition for the elimination of the interactions and nonlinearities in the mass properties is derived. The decoupled and invariant arm dynamics significantly reduces the complexity of controlling the direct-drive arm. In the latter half of the paper, a prototype robot developed on this basis is described. By using high torque brushless motors which were specially designed for the direct-drive robot, top speed and maximum acceleration were increased by an order-of-magnitude to about 10 m/s and 5 G, respectively.
Some New Developments in Fluidic Circuit Design
Authors: Drzewiecki T. M.
Published: July 2009

This paper presents several new developments in fluidic circuit design. The use of orifices and capillaries, as input and feedback resistors, and vice-versa, in an operational amplifier circuit is shown to result in a scaler whose gain varies either directly or inversely in proportion to kinematic viscosity. When operating on a temperature sensitive gainblock this scalar can be used to compensate for the effects of variable ambient temperature. The orifice formed by the space between a jet and a solid wall is a pressure sensitive resistance that is used as the controlling element in a gain changer and an automatically null-balanced Wheatstone bridge. In a novel use of a laminar proportional amplifier (LPA), the nonlinear saturation characteristic is used to linearize inversely nonlinear sensor and circuit outputs. Finally a set-point pressure sensor, that is a highly asymmetric LPA, is described that develops a high differential output pressure as a function of power jet pressure which can be some set-point pressure. By using this device as a pressure sensor, an ultra-quiet, high suppression performance pressure regulator has been built and demonstrated.