bluuebunny/crossref_metadata_2025 huggingface dataset:
Wall Heat Transfer and Storage Effects on the Thermal Dynamics of Otis-Effect Gas Compression Processes
Authors: Paynter H. M. , Fahrenthold E. P. , Rotz C. A.
Published: March 2008

Accurate and realistic modeling of the gas compression process in piston cylinder systems is of fundamental importance in various power and control applications. As a result, this dispersive-absorptive process (Otis, 1974; Pourmovahed and Otis, 1984; and Otis and Pourmovahed, 1985) has been analyzed in various theoretical and experimental studies, from both thermodynamic and system dynamics viewpoints. In a consistent extension of previous work to system boundaries characteristic of many practical devices, heat transfer and energy storage associated with the confining cylinder walls may be shown to exert a significant effect on the dynamics of the Otis-effect gas compression problem.
The Pumping Dynamics of a Positive Displacement Pump Employing Self-Acting Valves
Authors: Edge K. A. , Brett P. N.
Published: March 2008

The paper describes a general purpose digital computer model for the analysis of the pumping dynamics of positive displacement pumps employing self-acting valves. This model is verified by comparison with experimental tests on a diaphragm separator pump. Predicted and simulated cylinder pressure transients and inlet and delivery valve dynamics are compared over the complete pumping cycle. Close agreement between theory and experiment is achieved. The induction performance of the pump is examined in detail and the effects of operating conditions on volumetric efficiency are presented. The effect of inlet valve timing on delivery manifold pressure fluctuations is also discussed.
Adaptive Control of Multivariable Processes With Two Sampling Frequencies
Authors: Zhang Qiusheng
Published: March 2008

An adaptive control algorithm with two sampling frequencies was proposed in Zhang and Tomizuka (1988). The algorithm is less computationally intensive than regular adaptive control schemes when controlling those first-order multivariable industrial processes in which two groups of subsystems have separate time constants. In this case the steady-state errors are bounded by a deadzone. This note improves this result by using a better-designed deadzone, thus leading to smaller tracking errors.
An Explicit Minimum-Time Solution for the Simple Harmonic Oscillator
Authors: Choura Slim , Jayasuriya Suhada
Published: March 2008

It is well known that the minimum time control of a simple harmonic oscillator subjected to a bounded control input is a bang-bang control where the input cannot remain constant for more than half of the period of the oscillator. The necessary switching times for implementing such bang-bang control are usually determined by geometric means in the state-space, thus making it difficult to obtain the switchings and the final time for an arbitrary initial condition. An explicit solution for the switching times and the final time for a motion starting from an arbitrary initial state subjected to an arbitrary but constant input bound is developed for the simple harmonic oscillator. The explicit solution matches exactly the graphical solution (Athans and Falb, 1966).
Multi-Level Hypotheses Testing for Fault Detection in Continuous Process
Authors: Ray Asok
Published: March 2008

This paper presents the analytical development of a multi-level hypotheses testing algorithm and an extension of the sequential bi-level test procedure reported earlier [1]. The multi-level test procedure characterizes M distinct categories of faults in continuous processes like aircraft, spacecraft, and nuclear power plants, and is suitable for generating signals for early warning and failure. The test procedure has been implemented on a commercially available microcomputer for on-line detection of sensor faults in an operating nuclear reactor.
Hydraulic Servo-Control Analysis for Arc Furnace Electrode
Authors: Shichang Zhou , Xinming Cao , Guiyou Yao
Published: March 2008

An electric-arc furnace laboratory model was constructed and its characteristics under high temperature were studied. The response of the main hydraulic cylinder displacement with respect to step input was measured under high temperature conditions. The state equations of the system were set up by using bond graphs and its step response was computed. The computed results agree with the experimental results. The response of the main hydraulic cylinder controlled by a servo-valve along with a switching valve was also studied. Theoretical analysis and experiments indicate that if the appropriate closing voltage VK2 of the switching valve is selected, the step response of system will have the performance of small overshoot and settling time, and the response will be close to an ideal step form. The product of settling time ts and maximum overshoot MP is minimum is used as an objective function to determine the optimum VK2 which gives a satisfied step response.
Extended Bond Graph Representation of the Traction Problem in Linear Elastodynamics
Authors: Ingrim M. E. , Masada G. Y.
Published: March 2008

To illustrate the use of the extended bond graph notation, a reticulation is developed for a conjugate variable approximation of the traction problem in linear elastodynamics. This reticulation is general in the sense that all vector and tensor quantities are expressed using direct notation; that is, no specific coordinate system is chosen a priori. In addition, the only limitation placed upon the elasticity tensor C(X) is that it be symmetric. This allows homogeneous and inhomogeneous isotropic, orthotropic, etc., linearly elastic bodies to be modeled using these results. The conjugate approximations used here are entirely compatible with Galerkin based finite element methods. Consequently, this extended bond graph reticulation allows well-developed approximation techniques in solid mechanics to be directly incorporated into bond graph based system models.
Controllability and Observability of Distributed Gyroscopic Systems
Authors: Yang B. , Mote C. D.
Published: March 2008

Controllability and observability of a class of distributed gyroscopic systems under pointwise actuators and sensors are presented. The equations of motion are cast in a state space form, in which orthogonality of the eigenfunctions is obtained. The controllability and observability conditions in finite dimensions are obtained for a model representing a truncated modal expansion of the distributed system. In infinite dimensions the controllability and observability conditions are obtained through semi-group theory. In both the finite and infinite dimensional models the conditions of controllability and observability are evaluated through the eigenfunctions in an explicit form. The minimum number of actuators and minimum number of sensors needed to control and observe the system are determined by the largest eigenvalue multiplicity. The results are illustrated on vibration control of the axially moving string and the rotating circular plate.
State Estimation of the Nonself-Adjoint Acoustic Duct System
Authors: Hull A. J. , Radcliffe C. J. , MacCluer C. R.
Published: March 2008

The acoustic response of a hard walled duct with a partially absorptive boundary condition has been modeled in state space form. The system states of this model are not directly measurable. An observer is developed to obtain the state estimates. Numerical simulations are presented and convergence of the observer is discussed. Different integration schemes are compared and comments are made for eventual real-time application.
Dynamics of Human Legs Subjected to Posterior Impact
Authors: Wilson J. F.
Published: March 2008

This is a dynamic analysis of a three-mass, hinged beam model representing a standing human struck suddenly with a posterior, horizontal, step impact force. The results of parametric studies, presented in terms of nondimensional system variables, show the essential features of the dynamic moment responses in the lower leg. Included are the effects of the distribution of body mass, the location of the impact force, and the base fixity, with and without slip. Closed-form results show that the point of impact is not always the point of maximum bending moment on the lower leg. For step impact loads applied near the knee joint, peak moments are predicted near the midlength of the lower leg, the location coincident with about half of the observed fractures to the tibia and fibula of pedestrians struck by car bumpers near the knees.
A Prototype Steering Weave Stabilizer for Automobiles
Authors: Whitehead J. C.
Published: March 2008

A prototype high-speed steering stabilizer for automobiles applies transient steering torques so that the sum of natural steering restoring torque and the control torque is more nearly in phase with steer angle than the natural restoring torque alone. The resulting reduction in the phase lag from steer angle to restoring torque mitigates the steering weave mode. Since steering restoring torque is nearly proportional to vehicle lateral acceleration, weave controller circuitry could subtract instantaneous lateral acceleration from expected steady-state lateral acceleration calculated from steer angle and vehicle speed, and thence command a steering torque actuator depending on the difference signal. The prototype performs the same function using a concentrated mass on the lower steering wheel rim which is passively sensitive to both steer angle and lateral acceleration, thereby applying only transient steering torques in the desired manner at a vehicle speed of 30 m/s. The additional steering system inertia alone affects the weave mode, so a non-stabilizing configuration with the same mass distributed around the steering wheel rim is tested for direct comparison. The experimental data show a dramatic stabilization of weave for the configuration which applies control torque.
Dynamic Modeling and Analysis of Automotive Multi-Port Electronic Fuel Delivery System
Authors: Yang W. C. , Glidewell J. M. , Tobler W. E. , Chui G. K.
Published: March 2008

A dynamic model of a multi-port electronic fuel injection system, capable of analyzing fast fluid transients in the fuel, is presented. The model consists of distributed parameter models for fuel lines and lumped parameter models for the fuel pump, pressure regulator and injectors. Modal approximation is used to model fuel lines. An experimental test bench has been established, and comparison of simulation and experimental results shows excellent agreement in transient characteristics. Using this experimentally verified model, the effects of injector clogging and vapor in the fuel rail on pressure transients are examined. A bond graph model of the total system is presented to identify the proper formulation of each subsystem model.
Natural Dynamics of Robot Manipulators in the Presence of Obstacles
Authors: Jia T. , Amirouche F. M. L.
Published: March 2008

This paper presents the natural dynamic control problem of robot manipulators and its application to collision avoidance and path planning. A set of moving convex obstacles (or polyhedron) are modeled to achieve the desired conditions for collision detection and avoidance. The conditions represent a set of inequality constraints which are automatically incorporated to assure collision free motion. A minimum dimensional problem is achieved through the use of the null space of the Jacobian matrix associated with the constraint equations. A simple example to illustrate the procedures developed above is given.
Analysis and Design of Repetitive Control Systems Using the Regeneration Spectrum
Authors: Srinivasan K. , Shaw F.-R.
Published: March 2008

The absolute and relative stability of continuous-time SISO repetitive control systems is examined here using a function of frequency termed the regeneration spectrum. The regeneration spectrum is easily computed and is related to important features of the characteristic root distribution of such systems, for large values of the time delay. The regeneration spectrum is combined with other frequency domain measures of control system performance such as the sensitivity and complementary sensitivity functions to obtain improved insight into the tradeoffs in repetitive control system design. The result is a more rational approach to repetitive control system design and is illustrated by an example.
Vehicle Traction Control: Variable-Structure Control Approach
Authors: Tan Han-Shue , Chin Yuen-Kwok
Published: March 2008

A longitudinal one-wheel vehicle model is described for both anti-lock braking and anti-span acceleration. Based on this vehicle model, sufficient conditions for applying sliding-mode control to vehicle traction are derived via Lyapunov Stability Theory. With the understanding of these sufficient conditions, control laws are designed to control vehicle traction. Both the sufficient conditions and the control laws are verified using computer simulations.
Longitudinal Control of Automotive Vehicles in Close-Formation Platoons
Authors: Shladover S. E.
Published: March 2008

The capacity and safety of freeways can potentially be increased substantially if the vehicles are operated in platoons, using automatic longitudinal control systems to maintain very small spacings (of the order of 1 meter) between vehicles. This paper explains many of the technical considerations in the design of such control systems, employing a general nonlinear simulation model to develop quantitative results. The effects on control system performance of external forces, process and measurement noise, and sampling and quantization of measurements are shown. The importance of acceleration and jerk limits is demonstrated, and examples are used to illustrate how the control system must be designed to accommodate variations in the severity of the maneuvers it is expected to execute, as well as variations in propulsion system dynamics.
Experimental and Analytical Study of Pantograph Dynamics
Authors: Seering W. , Armbruster K. , Vesely C. , Wormley D.
Published: March 2008

A nonlinear, lumped parameter pantograph model including geometric and coulomb friction nonlinearities and variable stiffness has been developed. The model performance has been compared with experimental dynamic response data measured on a prototype pantograph. Responses of the model and the experimental data including subharmonic and harmonic resonances are in close agreement for motions excited by comparable forcing functions for input frequencies of 0 to 12 Hz. The model has been used to identify the primary parameters and nonlinear effects which influence dynamic pantograph performance.
Design of a Controlled Spatial Curve Trajectory for Robot Manipulations
Authors: Wu Chi-haur , Jou Chi-cheng
Published: March 2008

For integrating different constraints from robot’s tasks, such as geometry, kinematics, and dynamics, with trajectory planning and robot motion control, a two-layer robot trajectory planning structure is proposed. The structure decomposes the trajectory planning problem into path geometry planning and motion speed planning. By separating speed planning from path geometry planning, two different problems can be solved. The first problem is to incorporate geometric changes of a robot task into both translational and orientational path plannings. By solving it, various spatial curve paths can be planned and the difficulty of predicting rotational motions in the Cartesian space can be removed. The second problem is to incorporate motion constraints into the trajectory planning, such as the constraint of maintaining a desired constant robot speed along any planned geometric path. Through the proposed structure, different robot motion requirements along various spatial curves can be controlled by different speed control functions. To demonstrate the proposed scheme, examples are given.
Static and Dynamic Characteristics of a Two Stage Pilot Relief Valve
Authors: Shin Yung C.
Published: March 2008

Static and dynamic characteristics of a two stage relief valve have been studied theoretically and experimentally. The governing equations of the valve have been derived and sensitivity analysis was performed by digital computer simulation on the valve response characteristics based on the established dynamic equations of the motions of the valve. From this study, significant parameters on the valve response were identified, which can be modified to improve the dynamic characteristics of the valve. Subsequently, experiments were performed with a specially fabricated Vickers type pilot relief valve. The results showed fair agreement with the simulation results, thus proving the validity of the model.
Identifiability of Lagrangian Systems With Application to Robot Manipulators
Authors: Wang Qing-Guo
Published: March 2008

The deterministic parameter identifiability of mechanical linear and nonlinear dynamical systems is considered via linear parameterization of system Lagrangians and necessary and sufficient conditions are established on the identifiability for linear parameters. The identifiability condition results in a new concept, the irreducible Lagrangian representation, and it is introduced to characterize a system Lagrangian with the minimal number of identifiable parameters. A linear parameterization of the Lagrangians for n-degree-of-freedom robot manipulators with rotary joints is presented and, with the help of kinematic analysis, the irreducible representations are further obtained for the PUMA 560 and planar manipulators.
Adaptive Matching and Preview Controllers for Feed Drive Systems
Authors: Pak H. A.
Published: March 2008

The control scheme proposed aims to eliminate dynamic parameter mismatch between axes’ feed drives by using a single discrete time reference model of the feed drive speed regulation loop for all axes of a machine tool. In order to achieve this objective, the speed regulation loop for each axis is made adaptive using a direct approach. For contour tracking purposes, a preview feedforward controller (made possible through an N sample advanced reference word interpolator) is combined with a conventional state feedback control to form the input to the reference model.
Vector Bond Graph Analysis of Mechanical Systems
Authors: Fahrenthold E. P. , Wargo J. D.
Published: March 2008

The utility of existing bond graph methods in the analysis of complex mechanical systems has been limited significantly by the absence of a tensor based vector modeling methodology. Topological simplifications are needed in order to recapture the efficiency of graphical model formulation work for complex mechanisms. The needed simplifications can be achieved by the introduction of new bond graph structures which express in coordinate free form the momentum and energy balance relations and kinematic constraints commonly encountered in mechanical system dynamics.
Dynamics and Control of Robotic Systems Worn by Humans
Authors: Kazerooni H. , Mahoney S. L.
Published: March 2008

This article describes the dynamics, control, and stability of extenders, robotic systems worn by humans for material handling tasks. Extenders are defined as robot manipulators which extend (i.e., increase) the strength of the human arm in load maneuvering tasks, while the human maintains control of the task. Part of the extender motion is caused by physical power from the human; the rest of the extender motion results from force signals measured at the physical interfaces between the human and the extender, and the load and the extender. Therefore, the human wearing the extender exchanges both power and information signals with the extender. The control technique described here lets the designer define an arbitrary relationship between the human force and the load force. A set of experiments on a two-dimensional non-direct-drive extender were done to verify the control theory.
A Measurement Oriented Formulation of the Dynamics of Natural and Robotic Systems
Authors: Hemami H.
Published: March 2008

A measurement oriented formulation of rigid body dynamics is applied to a special class of planar linkage systems. It leads to a diagonal moment of inertia matrix, and thus simplifies the feedforward computations in the controller. On the other hand, if measurements are not available or measurements are not allowed, the computational burden shifts to the feedback computation of the generalized or internal forces. This formulation may find applications in off-line digital computer simulations and on-line control of the rigid body systems via the inverse dynamics methods. It may also underly computations in natural and biological systems that are rich with sensory modalities and processes. The computational burden in this model is shifted from the inverse of moment of inertia matrix to the derivation of the forces of constraint, contact, connection, internal or generalized. When these forces are available from measurements, the computations are indeed reduced and consequently on-line control problems are rendered easier. As a consequence of this representation the problems of transmission delay, and predictive compensation become important as is shown via an example. The investigation of the range of intermediate representations where computations and measurements are combined remains a fertile subject.
Dynamic Stability of a Girder Under Traveling Load Mass Systems
Authors: Aida T. , Green R.
Published: March 2008

When a multi-vehicle train passes over a railway bridge, it may be expected that a parametrically excited vibration occurs in the girders, due to the change in the additional mass distribution caused by the unsprung mass of the vehicles. An analytical method to determine the dynamic stability of thin-walled beams under a sequence of equidistant masses traveling at a constant speed is developed in this paper. In the numerical examples, it is shown that the magnitude of the unsprung mass of vehicles, the distance between them and the speed of the vehicles have a large effect on the parametrically excited unstable vibration of girders. The dynamic stability of a simply supported railway bridge is clarified using the above method.
Analysis of a Permanent Magnet Levitation Actuator With Electromagnetic Control
Authors: Nagaya K. , Arai N.
Published: March 2008

This paper proposes an actuator in the magnetic levitation system using a permanent magnet and an electromagnet. In this system, the gravity force of the masses is supported by a strong permanent magnet in which two identical poles face each other. The vibration due to external disturbances is controlled by use of the electromagnet by changing magnetic fluxes of one of the permanent magnets. The analytical expressions for obtaining the levitation force, spring constant, and the control force versus the electric current in the electromagnet were derived using the equation of the electromagnetic theory. Numerical simulations under the control using the optimal regulator for the magnetically levitated body were carried out. To verify the present theoretical results, experimental results were also obtained.
Distributed Modal Identification and Vibration Control of Continua: Theory and Applications
Authors: Tzou H. S.
Published: March 2008

Conventional transducers and actuators are “discrete” in nature, i.e., they usually measure and control spatially discrete locations. These discrete devices become useless when they are placed at modal nodes or lines. In this paper, a generic “distributed” modal identification and vibration control theory for sensing and control of continua, e.g., shells, plates, cylinders, beams, etc., is proposed. The generic theory is derived for a thin shell coupled with two electroded piezoelectric layers. One piezoelectric layer serves as a distributed sensor and the other a distributed actuator. The sensor output, or a reference signal, is processed, amplified, and fed back into the distributed actuator. Due to the converse effect, the injected high voltage induces in-plane strains which result in counteracting moments used to suppress the shell oscillation. System dynamic equations and state equations are also derived. The theory shows that the distributed sensor can identify all vibration modes and the distributed actuators also control all modes. Simplification of the generic theory to other geometries is also demonstrated.
Zero Phase Error Tracking Control for Square Sampled-Data Systems
Authors: Pak H. Ali , Li G. Q.
Published: March 2008

A multivariable version of the zero phase error tracking control algorithm is presented for sampled-data systems. The feedforward controller is based on the minimal-order inverse of a square system’s transfer function matrix. It is shown that, apart from phase cancellation, complete input/output decoupling will result from the use of the controller. Using a simulation study, the control algorithm’s performance is demonstrated for a multivariable positioning system.
On Discrete-Time Feedforward Asymptotic Tracking Controllers
Authors: Pak H. A. , Shieh Rowmau
Published: March 2008

A feedforward design formulation for asymptotic tracking controllers is presented for linear multivariable systems under discrete-time control. The control scheme is based upon the use of future set points along reference trajectories with known models. One advantage of the control scheme is that it does not require the derivative states of the reference trajectory explicitly during its operation. As a result, apart from numerical noise reduction, the autonomous trajectory generation algorithms need not be tightly coupled to the control algorithm for purpose of real time execution.
Quantitative Design of Mimo Nonlinear Uncertain Feedback Systems Having Nonzero Initial Conditions
Authors: Yaniv Oded
Published: March 2008

An n × n nonlinear uncertain multiple-input multiple-output plant W, known only to belong to a set {W} is considered. At t=0 it is transformed into a one-degree-of-freedom feedback structure with compensation G. A synthesis method is developed to design G so that a given level of attenuation of plant output is attained for all Wε{W} and for any set of initial conditions y0ε{y0} on output of the plant W. The design philosophy is to convert the problem into a disturbance attenuation problem for uncertain linear time invariant systems with zero initial state, which in turn is converted into a series of successive single-input-output problems of the disturbance attenuation type. A design example is included.
Time Optimal Seek Trajectories for a Dual Stage Optical Disk Drive Actuator
Authors: McCormick J. , Horowitz R.
Published: March 2008

A closed-form solution for the time optimal control of a dual actuator disk drive system that takes into account the physical constraint limiting the relative motion of the fine and coarse actuator has been derived. The result is useful for determining track seeking strategies for high performance optical disks. The application of the necessary conditions to a simplified model of the compound actuator is presented and a solution derived.
Sliding Mode Fuel-Injection Controller: Its Advantages
Authors: Cho Dan , Hedrick J. Karl
Published: March 2008

New and improved results are presented on the advantages of employing the sliding mode control method for designing a closed-loop fuel-injection system. The two biggest advantages of this method are: (1) its compatibility with the current oxygen sensor technology and (2) its ability to consider robustness and performance issues analytically for an automotive engine, whose operating characteristics are highly complex and nonlinear. The controller can achieve the stoichiometric ratio control of air and fuel with excellent transient properties and is robust to model errors and disturbances. Furthermore, through direct comparisons to PI-controllers, it is shown that the sliding mode fuel-injection controller is versatile and requires very little tuning time. Performance evaluations are performed both on an engine-only model and on a comprehensive powertrain model that includes automatic transmission and drivetrain dynamics.
Application of a Nonlinear Self-tuning Controller for Regulating the Speed of a Hydraulic Turbine
Authors: Wang H. , Liu Y. Q. , You D. H.
Published: March 2008

This paper presents an application of a modified self-tuning controller for regulating the speed of the hydraulic turbine ZZ-105-HL. First the self-tuning algorithm developed in [1] and [5] is extended so that the measurable operating points of the turbine can be used to increase the convergence rate of the online identification. A robust controller is then constructed by combining the identification algorithm within the structure of a robust controller so that asymptotic stability and perfect tracking are realized.
Stability of Uncertain Linear Systems With Time Delay
Authors: Youcef-Toumi K. , Bobbett J.
Published: March 2008

The control of systems with uncertain dynamics and unpredictable disturbances has raised some challenging problems. This is particularly important when high system performance is to be guaranteed at all times. Recently, Time Delay Control has been suggested as an alternative control scheme. The proposed control system does not require an explicit plant model nor does it depend on the estimation of specific plant parameters. Rather, it combines adaptation with past observations to directly estimate the effect of the plant dynamics. This paper outlines the Time Delay Control law for a class of linear dynamic systems and then presents a sufficient condition for stability of linear uncertain systems with time delay. The ideas of Nyquist and Kharitonov are used in the development of a sufficient condition, which does not resort to using approximations for time delay. Like Nyquist, the condition depends on maps of the Nyquist path and, like Kharitonov, stability depends on four functions each yielding a stable system. In this paper we combine these ideas to determine the stability of systems where the Time Delay Controller is applied to single input single output, linear time-invariant plants whose coefficients are known to vary within certain defined intervals. The development is carried out in the context of Time Delay Control but it can be applied in more general cases. Two examples will illustrate the approach and the usefulness of the technique.
Robust Control of Generalized Dynamic Systems Without the Matching Conditions
Authors: Qu Zhihua , Dorsey John
Published: March 2008

A general control law and a set of conditions are proposed to guarantee the stability of dynamic systems with bounded uncertainties. The results do not require the matching conditions on the uncertainties and subsume several existing results as special cases. Moreover, it is shown that there is at least one class of uncertain dynamic systems which can always be stabilized under the proposed control law no matter what the size and the structure of the input-unrelated uncertainties.
Design of Dual-Range Linear Controllers for Nonlinear Systems
Authors: Nassirharand A.
Published: March 2008

A new procedure for synthesis of dual-range linear controllers for use with highly nonlinear, deterministic, time-invariant, and single-input single-output systems in a unity feedback configuration is developed. The procedure uses a factorization approach coupled with optimization which is used to parameterize and search the class of all stabilizing controllers for linear systems with integrity. The objective of the synthesis approach is to arrive at robust closed-loop systems that are solutions to the closed-loop model matching problem. The procedure is presented in an algorithmic form, and it is demonstrated via example problems. The results are compared with those previously obtained using a frequency domain approach.
A Stochastic Regulator for Integrated Communication and Control Systems: Part II—Numerical Analysis and Simulation
Authors: Liou Luen-Woei , Ray Asok
Published: March 2008

A state feedback control law has been derived in Part I [1] of this two-part paper on the basis of an augmented plant model [2, 3, 4] that accounts for the randomly varying delays induced by the network in Integrated Communication and Control Systems (ICCS). The control algorithm was formulated as a linear quadratic regulator problem and then solved using the principle of dynamic programming and optimality. This paper, which is the second of two parts, presents (i) a numerical procedure for synthesizing the control parameters and (ii) results of simulation experiments for verification of the above control law using the flight dynamic model of an advanced aircraft. This two-part paper is concluded with recommendations for future work.
Process Fault Diagnosis Based on Process Model Knowledge: Part I—Principles for Fault Diagnosis With Parameter Estimation
Authors: Isermann R. , Freyermuth B.
Published: March 2008

A computer assisted fault diagnosis system (CAFD) is considered which allows the early detection and localization of process faults during normal operation or on request. It is based on an on-line engineering expert system and consists of an analytic problem solution, a process knowledge base, a knowledge acquisition component and an inference mechanism. The analytic problem solution uses a process parameter estimation, and the detection of process coefficient changes, which are symptoms of process faults. The process knowledge base is comprised of analytical knowledge in the form of process models and heuristic knowledge in the form of fault trees and fault statistics. In the phase of knowledge acquisition the process specific knowledge like theoretical process models, the normal behavior and fault trees, is compiled. The inference mechanism performs the fault diagnosis, based on the observed symptoms, the fault trees, fault probabilities and the process history. This is described in Part I. In Part II case study experiments with a d.c. motor, centrifugal pump, a heat exchanger, and an industrial robot show practical results of the model based fault diagnosis.
Robust Nonlinear Stick-Slip Friction Compensation
Authors: Southward S. C. , Radcliffe C. J. , MacCluer C. R.
Published: March 2008

A nonlinear compensation force for stick-slip friction is developed to supplement a proportional + derivative control law applied to a one-degree-of-freedom mechanical system. Inertial control objects acted on by stick-slip friction are common mechanical components in mechanical servo systems and the conceptual model chosen for this investigation is a mass sliding on a rough surface. The choice of a discontinuous compensation force is motivated by the requirement that the desired reference be a unique equilibrium point of the system. The stick-slip friction force, modelled with a sticking force term and a slipping force term, generates discontinuous state derivatives. A Lyapunov function is introduced to prove global asymptotic stability of the desired reference using a modification of the direct method for discontinuous systems. Stability is verified numerically as well as experimentally. The nonlinear compensation force is robust with respect to the character of the slipping force which is assumed to lie within a piecewise linear band. Exact knowledge of the static friction force levels is not required, only upper bounds for these levels. Stability and control effectiveness is verified analytically, numerically and experimentally on a laboratory test stand.
State Space Representation of the Open-Loop Dynamics of the Space Shuttle Main Engine
Authors: Duyar Ahmet , Eldem Vasfi , Merrill Walter C. , Guo Ten-Huei
Published: March 2008

A parameter and structure estimation technique for multivariable systems is used to obtain state space representation of open loop dynamics of the space shuttle main engine (SSME). The parametrization being used is both minimal and unique. The simplified linear models may be used for fault detection studies and control system design and development.
Rohrs Examples and Robustness of Simple Adaptive Control
Authors: Bar-Kana Izhak
Published: March 2008

It is well known that arbitrary pole-placement can be obtained when controllers of the same order as the plant to be controlled are used. For this reason, the blame for the failure of low-order adaptive controllers was put on the unmodeled dynamics. This paper reconsiders some well known examples to show that the previous conclusions were too pessimistic, and that low-order adaptive controllers are fit to control the given plants.
An Implicit Quadratic H∞ Self-Tuning Controller
Authors: Hashim R. A. , Grimble M. J.
Published: March 2008

An implicit H∞ self-tuning control scheme is presented. Costing of the system error and control signals is achieved using a dynamic cost function. The H∞ optimal solution to this problem is obtained using a recursive least square identification algorithm. The simple procedure for calculating the controller, without solving any diophantine equations, make this method particularly suitable for self-tuning control applications.
A Comparison of Analytical and Experimental Performance Data for a Two-Axle Freight Car
Authors: Bailey J. R. , Wormley D. N.
Published: March 2008

The dynamic performance of a two-axle lightweight freight car has been determined through a combined analytical and experimental program. A fourteen degree of freedom vehicle model has been developed, employing nonlinear damping and stiffness suspension elements and nonlinear geometric and creep force wheel/rail interaction models. Analytical results have been compared with experimental field test data. Dynamic vehicle simulations agree closely with field test data for operation on vertical and crosslevel perturbed track. Simulations of the vehicle operating on curved and laterally perturbed track are in reasonable agreement with field test data in predicting performance trends for conditions approaching wheel climb derailment limits. Precise predictions of vehicle performance under wheel flanging conditions require detailed knowledge of local wheel/rail profiles and friction level.
The Variable Fulcrum Isolator: A Low Power, Nonlinear, Vibration Control Component
Authors: Margolis D. L. , Baker D.
Published: March 2008

A nonlinear, controllable vibration isolation device—the Variable Fulcrum Isolator (VFI)—is introduced. Methods of designing feedback control laws are presented. Computer simulations compare the rms acceleration and control power of the VFI with equivalent passive and linear active systems. The VFI achieves performance equal to the linear active system with less power for inputs composed of a small number of discrete frequencies. For very noisy inputs or for high performance systems which demand high control power, the linear active system is eventually superior. It is suggested that further study of the feedback system will yield improvement in these cases.
Achieving a Variable Flow Supply by Controlled Unloading of a Fixed-Displacement Pump
Authors: Tomlinson S. P. , Burrows C. R.
Published: March 2008

This paper addresses the operational performance of a fixed-displacement pump controlled by an unloading valve to provide a fluctuating flow source. This approach should be cheaper and more efficient than the use of a variable-displacement unit. Computer simulation is used to predict the performance of the system and act as a guide in optimizing the control system. An experimental rig has been constructed to examine the practicalities of these ideas. Some experimental results are presented. Future work will be concerned with noise and efficiency studies.
A Stability Model for Flexible Rotors With Magnetic Bearings
Authors: Maslen E. H. , Bielk J. R.
Published: March 2008

A direct linear modeling scheme is described for magnetic bearing supported rotors. The model includes the effect of controller bandwidth as well as sensor-actuator noncollocation. These effects, commonly ignored in simpler formulations, can have substantial impact on system stability. Based on a first order matrix differential equation form, the model is very suitable for stability analysis using widely available computer software.
Stability Criterion For Linear Oscillatory Parabolic Systems
Authors: Hong Keum S. , Bentsman Joseph
Published: March 2008

This paper presents a stability criterion for a class of distributed parameter systems governed by linear oscillatory parabolic partial differential equations with Neumann boundary conditions. The results of numerical simulations that support the criterion are presented as well.
Decentralized Robust Control for Large-Scale Uncertain Systems: A Design Based on the Bound of Uncertainty
Authors: Chen Y. H.
Published: March 2008

A class of large-scale linear uncertain systems is under consideration. The uncertainty is time-varying. No a priori deterministic or stochastic information is assumed except its possible bound. Decentralized robust control for each subsystem is proposed. The salient feature of the design is that it decomposes the internal uncertainty and the interconnection. This enables the structural property of the uncertainty to be incorporated in the design. An adaptive version of the decentralized robust control is also proposed as no input matrix uncertainty appears.
Structural Identification Using Order Overspecified Time-Series Models
Authors: Hollkamp J. J. , Batill S. M.
Published: March 2008

An identification method that uses order overspecified time-series models and a truncated singular value decomposition (SVD) solution is studied. The overspecified model reduces the effects of noise during the identification process, but produces extraneous modes. A backwards approach coupled with a minimum norm approximation, using a truncated SVD solution, enables the system modes to be distinguished from the extraneous modes of the model. Experimental data from a large flexible truss is used to study the effects of varying the truncation of the SVD solution and an order recursive algorithm is used to study the effects of model order. Results show that the SVD may be ineffective in separating the data into signal and noise subspaces. However solutions for highly overspecified model orders exhibit solution properties similar to the minimum norm solution and system and computational modes can be discriminated without a truncated solution.
Application of Floquet Theory to On-Off Valve Controlled Pneumatic Actuators
Authors: Kunt Cengiz , Singh Rajendra
Published: March 2008

A periodic linear time varying (LTV) model for on-off valve controlled pneumatic actuation systems, was described in an earlier paper by the authors. Based on this LTV model formulation, Floquet’s Theorem is invoked to characterize dynamic response of the system. A new computational technique called the expanded state space method is developed to calculate the frequency response of the LTV system with staircase coefficient variations. This technique is computationally superior to the straightforward solution scheme. Floquet Theory is also used to assess the nature of transient response. A single acting cylinder system controlled by an on-off valve is considered to illustrate the stability and transient response issues. Computer simulation based on the nonlinear model is used to obtain detailed results. It is shown that application of the Floquet Theory provides valuable insight into the dynamic response of the class of actuators considered.
Dynamic and Steady-State Analysis of an Auto-Regulator in a Flow Divider and/or Combiner Valve
Authors: Fedoroff M. , Burton R. T. , Schoenau G. J. , Zhang Y.
Published: March 2008

Flow divider and/or combiner valves are hydraulic components which are used to divide and/or combine flow in a predetermined ratio independent of loading conditions. Over the past years the authors have successfully designed valves which can divide and/or combine flow with an error of less than 3 percent for all loading conditions. More recently, a valve which can be used to divide and combine flow for a wide range of flow requirements and still maintain an error of less than 3 percent has been developed and has been labeled an “auto-regulated high precision flow divider/combiner valve”. The heart of the auto-regulated valve is the autoregulator itself. In this paper, the operation of the regulator is discussed and design criterion for acceptable performance presented. A linearized model is developed from which a number of valve parameters are established. A more complex model using the Power Bond Graph technique is presented, and transient responses to different flow inputs are compared to experimental data. The model and experimental responses were in good agreement; hence, it was concluded that the model could be used with confidence in future stability studies.
Robust Tracking Control for Robots With Bounded Input
Authors: Novakovic´ Z. R.
Published: March 2008

A novel approach to robust tracking control synthesis is presented. Information about the input (control) constraints is fully exploited to achieve a simple algorithm, independent of the extent of model uncertainty. The control law is accelerometer-free (or even tacho-free, also), robust to sensor noise and allows the prespecification of the error decay rate. It is realistic from the engineering standpoint and can be implemented using current microprocessor technology. Practical tracking is proved by means of Lyapunov methodology. A simulation illustrates the effectiveness of the proposed approach.
Extended Bandwidth Zero Phase Error Tracking Control of Nonminimal Phase Systems
Authors: Torfs D. , De Schutter J. , Swevers J.
Published: March 2008

This paper describes a new feedforward algorithm for accurate tracking control of nonminimal phase systems. Accurate feedforward calculation involves a prefilter design using the inverse system model. Nonminimal phase systems cause problems with this prefilter design, because unstable zeros become unstable poles in the inverse model. The zero phase error tracking control algorithm (ZPETC) consists of a substitution scheme, which removes the unstable zeros. This scheme introduces a small gain error, which increases with frequency, but no phase error. This paper investigates additional properties which give more insight into the ZPETC algorithm, and allow to improve it. The improved algorithm is based on the same substitution scheme as ZPETC, but adds additional feedforward terms to compensate for the gain error. These additional terms increase the frequency range for which the overall transfer function has only limited gain error, without introducing phase errors. The additional feedforward terms repeatedly reduce the tracking error proportional to ε2, ε4, ε6, …, where ε is the ZPETC tracking error. The new feedforward algorithm or new substitution scheme is therefore called “extended bandwidth zero phase error tracking control algorithm” (EBZPETC). Experimental results on a one-link flexible robot compares both methods.
Control Under Uncertainty Through Zone Logic
Authors: Egilmez K. , Kim S. H.
Published: March 2008

The manufacturing plant represents a complex environment, rife with uncertainty. The complexity arises from the multitude of interactions that must be considered when attempting to model most manufacturing processes. Important process variables can remain unidentified; or even if they are identified, their interactions may remain uncertain. This complexity and the uncertainties that are often its derivatives cause various inefficiencies when conventional control methods are employed. In an attempt to remedy this situation, an intelligent control methodology termed zone logic has been advanced. Various extensions to it have been proposed which are designed to increase its domain of applicability. This paper further extends zone logic into the area of stochastic controls by using concepts from Bayesian belief networks. An information theoretic analysis of an initial application of stochastic zone logic is performed. This analysis indicates that an object oriented computational scheme best matches the real-time performance requirements for knowledge-based control systems.