bluuebunny/crossref_metadata_2025 huggingface dataset:
Generalized Vector-Network Formulation for the Dynamic Simulation of Multibody Systems
Authors: Richard M. J. , Anderson R. , Andrews G. C.
Published: July 2009

This paper describes the vector-network approach which is a comprehensive mathematical model for the systematic formulation of the nonlinear equations of motion of dynamic three-dimensional constrained multi-body systems. The entire procedure is a basic application of concepts of graph theory in which laws of vector dynamics have been combined. The main concepts of the method have been explained in previous publications but the work described herein is an appreciable extension of this relatively new approach. The method casts simultaneously the three-dimensional inertia equations associated with each rigid body and the geometrical expressions corresponding to the kinematic restrictions into a symmetrical format yielding the differential equations governing the motion of the system. The algorithm is eminently well suited for the computer-aided simulation of arbitrary interconnected rigid bodies; it serves as the basis for a “self-formulating” computer program which can simulate the response of a dynamic system, given only the system description.
Optimal Control of a General Environmental Space
Authors: Townsend M. A. , Cherchas D. B. , Abdelmessih A.
Published: July 2009

This study considers the optimal control of dry bulb temperature and moisture content in a single zone, to be accomplished in such a way as to be implementable in any zone of a multi-zone system. Optimality is determined in terms of appropriate cost and performance functions and subject to practical limits using the maximum principle. Several candidate optimal control strategies are investigated. It is shown that a bang-bang switching control which is theoretically periodic is a least cost practical control. In addition, specific attributes of this class of problem are explored.
Real Time Computer Control of a Quadruped Walking Robot
Authors: Lee Tsu-Tian , Shih Ching-Long
Published: July 2009

This paper presents a description of the hardware and software systems used to achieve real-time computer control of locomotion in an experimental quadruped walking robot. This robot possesses three independently powered joints in each of its four legs. Each joint provides position and rate feedback to a microprocessor-based controller. To control the movement of the leg so that the leg is placed on the desired foothold position, nonlinear feedback is first applied for decoupling, and then Model-Reference-Adaptive-Control is used to control the motion and position of the leg. Experimental results show that the proposed control algorithm can effectively control the leg.
An Approach to Automated Deburring by Robot Manipulators
Authors: Kazerooni H. , Bausch J. J. , Kramer B. M.
Published: July 2009

The deburring process of manufactured parts has been investigated theoretically and experimentally as a frequency domain control problem with special regard to application by industrial robot manipulators. A new control strategy has been developed for precision deburring to guarantee burr removal while compensating for robot oscillations and small uncertainties in the location of the part relative to the robot. Compliant tool-holders, designed according to the above control strategy, provide the required normal and tangential forces for deburring. A servo positioning table used to holds parts, has been considered in this study to compensate for robot oscillations up to 80 percent. The robot, the compliant tool-holder, and the servo positioning table, working together with a closed-loop process control, form a new automated system that deburrs manufactured parts.
Optimal Tracking Controller Design for Invariant Dynamics Direct-Drive Arms
Authors: Pak H. A. , Turner P. J.
Published: July 2009

This paper presents an optimal solution to the problem of tracking controller design for a category of direct-drive robot arms, mechanically constructed to have invariant and decoupled joint actuator dynamics. The controller acts on joint actuators consisting of d.c. servo motors driven via servo amplifiers containing an analog current feedback loop. For good tracking behavior, the controller uses future reference positions of a joint to anticipate the changes in reference velocity. An explicit acceleration feedforward term is avoided improving the power to noise ratio of the control signal. For good regulation behavior, the controller uses position and velocity feedback. An integral of error term is also avoided, reducing the probability of the occurrence of limit cycle oscillations caused by saturation of the actuator torque rating. The correlations between the classical and the optimal design parameters are discussed using transient response analysis followed by experimental observations.
Reduced Conservatism in the Ultimate Boundedness Control of Mismatched Uncertain Linear Systems
Authors: Yedavalli Rama K. , Liang Z.
Published: July 2009

This paper addresses the aspect of the control of uncertain linear systems based on the theory of ultimate boundedness. A similarity transformation on the original system is proposed which yields a better decomposition of the matched and mismatched parts and/or a less conservative bound on the mismatched perturbation. The proposed method can be applied to both zero as well as nonzero set point control. A simple example is presented to illustrate the proposed methodology.
On the Robustness of Mismatched Uncertain Dynamical Systems
Authors: Chen Y. H.
Published: July 2009

We consider the robustness problem of uncertain dynamical systems which do not satisfy the so-called matching conditions. We employ the controls which assure practical stability of the associated matched dynamical system. After introducing the idea of measure of mismatch, various conditions are stated, whose satisfaction assures that the mismatched uncertain system is practically stable under such a control. We also show that, under certain conditions, uniform attractivity can be assured; this has the advantage of reducing the measure of mismatch, and hence places lesser restrictions on the allowable magnitude of the uncertainty.
The Design of Radial Vortex Amplifiers for High Performance Power Fluidics
Authors: King C. F.
Published: July 2009

This paper presents a design algorithm for radial vortex amplifiers. The algorithm allows radial vortex amplifiers to be designed for high performance in terms of Turn Down Ratio and Cutoff Control Pressure Ratio and for low levels of internally generated noise. Devices designed through this algorithm give significant improvments on the envelope of previously published best designs.
Adaptive Control of the Fluid Heat Exchange Process
Authors: Harrell R. C. , Kranzler G. A. , Hsu C. S.
Published: July 2009

An adaptive algorithm for controlling the fluid heat exchange process via flowrate manipulation was presented. The algorithm utilized a model reference structure based on a linear time-variant approximation of the bilinear process dynamics. Adaptive feedforward and feedback compensation was provided. The control law was implemented on an evacuated tube solar water heating system. Experimental results demonstrated the ability of the adaptive scheme to accurately control collector fluid temperature under severe variations in solar insolation.
Structural Parameter Identification in the Frequency Domain: The Use of Overdetermined Systems
Authors: Braun S. G. , Ram Y. M.
Published: July 2009

This paper deals with the fitting of a rational function to an experimentally determined frequency domain transfer function. Examples show that the use of overdetermined fitted systems improve the identification in noisy situations. A method is presented, enabling the determination of the number of zero/poles of the system, and the relation to the rank of the matrix used in a least square identification method.
Computation of Rigid-Body Angular Acceleration From Point-Acceleration Measurements
Authors: Angeles Jorge
Published: July 2009

The computation of the angular acceleration of a rigid body from measurements of accelerations of three noncollinear points of the body is presented in this paper. This is based on algorithms presented previously for the computation of the orientation and the angular velocity of a rigid body from measurements of position and velocity of three noncollinear points of the body. Moreover, compatibility conditions that the said point measurements should verify are introduced. These are necessary to verify the rigidity assumption on the one hand; on the other hand, they are introduced as a means of filtering roundoff and/or measurement errors, which is particularly useful if redundant measurements are taken, i.e., on more than three points. The procedure is illustrated with a fully solved example.
Nonlinear Control of a Distributed System: Simulation and Experimental Results
Authors: Plump J. M. , Hubbard J. E. , Bailey T.
Published: July 2009

A nonlinear active vibration damper has been developed which uses a spatially distributed piezoelectric actuator, polyvinylidene flouride, to achieve active vibration control of a cantilever beam. The control algorithm was derived using Lyapunov’s Second Method. All modes of the beam can be controlled simultaneously if the angular velocity of the tip of the beam is known. A simulation algorithm was developed to predict the effect of the control on the free decay of a single mode. A parameter study for the first mode was performed and compared to experimental results. The active damper has been tested successfully on two different scale structures.
An Algorithm for Obtaining Bang-Bang Control Laws
Authors: Wen J. , Desrochers A. A.
Published: July 2009

Bang-bang control problems have long been of interest to control engineers. Much of the theoretical study of these problems has been limited to linear systems and the results are usually problem-specific. This paper presents a new computational method for solving control problems when it is desired that the control action be bang-bang. A gradient-based algorithm is developed where the switching times are updated to minimize the final state missed distance. The algorithm explains how a change in a switching time propagates through the other switching times and affects the final state. The algorithm is applicable to linear and nonlinear problems, including multi-input systems.
Modal Control of Fast Large-Scale Robot Motions
Authors: Stepanenko Y.
Published: July 2009

This study concentrates on the following topics in linear state-feedback robotic control: an algorithm for the generation of linearized robot models, a control law providing a desired eigenstructure for the linearized models, and the eigenvalue sensitivity to changes of the linearized model parameters. The algorithm allows the computer generation of linearized dynamic models for any articulated mechanism with revolute or prismatic joints. It does not include numerical differentiation and is based on a compound-vector technique and Newton-Euler dynamics. The control law allows the arbitrary assignment of all eigenvalues and certain entries of the closed-loop eigenvectors. The general structure of the closed-loop modal matrix and the flexibility available in eigenvector assignment are considered. A sensitivity analysis is given for the decoupled control law resulting from a particular eigenvector assignment. An experimental vertion of the developed modal controller was implemented on a multiprocessor system based on Motorola 68020 microprocessors. Details of the implementation and results of robot motion simulation are also included.
A New Approach to Adaptive Control of Manipulators
Authors: Seraji H.
Published: July 2009

The paper presents a new approach to adaptive control of manipulators to achieve trajectory tracking by the joint angles. The central concept in this approach is the utilization of the manipulator “inverse” as a feedforward controller. The desired trajectory is applied as an input to the feedforward controller which “behaves” as the “inverse” of the manipulator at any operating point; and the controller output is used as the driving torque for the manipulator. The controller gains are then updated by an adaptation algorithm derived from MR AC theory to cope with variations in the manipulator inverse due to changes of the operating point. An adaptive feedback controller and an auxiliary signal are also used to enhance closed-loop stability and to achieve faster adaptation. The proposed control scheme is computationally fast and does not require a priori knowledge of the complex dynamic model or the parameter values of the manipulator or the payload. Simulation results are presented in support of the proposed adaptive control scheme. The results demonstrate that the adaptive controller performs remarkably well for different reference trajectories and despite gross variations in the payload.
A Heuristic Study of Relegation of Control in Constrained Robotic Systems
Authors: Hemami H. , Wongchaisuwat C. , Brinker J. L.
Published: July 2009

A major control problem in the robotic field is the simultaneous and independent control of constrained trajectories and forces of constraint. The trajectories and the forces are related through the mechanical structure of the system. The task of the controller is to influence the mechanical coupling and allow separate control of the trajectories and the forces. A feasible control strategy is by relegation of control to the state or to the input. Relegation by inputs implies assigning the control of trajectories and forces to independent groups of inputs. In this paper, exact and approximate input relegation strategies are investigated. The effectiveness of the input relegation strategy is tested by digital computer simulation of a three link planar robot in a periodic rubbing maneuver.
Application of Reduced Order Model to Automotive Engine Control System
Authors: Kamei E. , Namba H. , Osaki K. , Ohba M.
Published: July 2009

This study deals with a multivariable automotive engine control system using a reduced order model. The system controls the engine torque and air fuel rate (A/F) simultaneously using linear quadratic (LQ) control theory. The mathematical model is obtained using a statistical identification method. The instrumental variable method is employed to estimate the parameters of the mathematical model. This model is reduced to an eighth-order one using minimal realization. A 16-bit microprocessor is employed for actual contruction of the control system, and a step response test was conducted. As a result, the system yielded a response similar to the simulation results.
Robot Path Planning in Three-Dimensions Using the Direct Subspace
Authors: Red W. E. , Troung-Cao H. V. , Kim K. H.
Published: July 2009

An efficient subspace approach is used to find collision-free paths in congested workspaces for a general class of robots having revolute and/or prismatic joints. A three-dimensional joint space is formed by mapping the workspace obstacles represented by polyhedral elements into the robot’s primary degrees-of-freedom comprising the first three robot links, also modeled by polyhedral elements. In this approach the secondary degrees-of-freedom (>3), including objects grasped by the robot end-effector, are bounded by a box attached to the distal primary link. The joint space obstacles represent forbidden space that limits the allowable robot configurations. Paths are then planned on a two-dimensional direct subspace of the joint space using graphics cursor input. Methods of iteration elimination are used to reduce the computational time required to transform obstacles into the joint space.
Estimator for Dynamic System Using Operating Records
Authors: Smith Otto J. M.
Published: July 2009

An instrumental variable estimation of the parameters of an unknown system is augmented with several additional computations and compared with a least squares estimation. Good results follow from the addition of the following. 1. The mean of the additive uncorrelated noise is a variable included in the list of unknown coefficients to be estimated. 2. Convergence is in the domain of poles and residues, not coefficients of polynomial representation of Laplace or sampled-data transforms or differential or difference equations. 3. The estimation is at least three more than the expected system order. 4. The estimated system model is constrained to be stable and is used to generate the instrumental variables. 5. The initial state (initial conditions) is estimated and used in the model. 6. Iterative sequential recursive estimations are necessary. Bootstrapping is used to obtain the noise vector. 7. When the equation error (residual) is relatively small, the residual is noise, not estimated model error, and the instrumental variable method minimizes the cross-correlation between the noisy residual and the noise-free state variables (instrumental variables) derived from the noise-free model. The residual is not minimized by least squares, which would create a large bias in the estimates.
Force Sensing in Magnitude, Direction, and Position
Authors: Martin K. F. , Lockman H.
Published: July 2009

A sensing device is described which measures the magnitude, direction, and position of force in the plane of the sensor. The basic sensing method is by strain gauge bridges, the outputs of which are amplified and fed via Analogue to Digital (A/D) converters to a microcomputer for calculation of the force characteristics. The transducer system is shown to be capable of measuring quasi static forces; experimental measurements confirming the feasibility of the device. Further research work is planned to improve the accuracy of the system and to ascertain and improve its capability of measuring dynamic forces.
Controlling Impact Forces in Pneumatic Robot Hand Designs
Authors: Parker J. K. , Paul F. W.
Published: July 2009

Robot hands capable of applying controllable forces to a wide variety of objects would increase the number of robotic applications in manufacturing. One frequently overlooked part of the force control problem is the initial impact between the robot hand “finger” and the object. Experimentally determined impact forces for a variety of hand fingertip and object surface stiffnesses are presented. Impact forces predicted from low order, lumped parameter linear models are also presented for comparison. These results are used to justify velocity control as the means for reducing impact forces. Minimum time optimal control of a robot hand finger with a zero final velocity constraint would give rapid grasping with zero impact force between the finger and object. Experimental and numerical optimal control results for a pneumatically actuated finger are presented. A proof-of-concept robot hand which implements a “near-optimal” control strategy for grasping objects at imprecisely known locations is presented and discussed with experimental results.
Adaptive Zero Phase Error Tracking Algorithm for Digital Control
Authors: Tsao Tsu-Chin , Tomizuka Masayoshi
Published: July 2009

This paper describes an adaptive feedforward controller to let the output of a plant with stable and unstable zeros track a time varying desired output. The dynamics of the closed loop system consisting of the plant and the feedback controller are assumed unknown or slowly varying due to changes on the plant parameters. In the control scheme proposed in this paper, the feedforward controller is adaptive while the feedback controller is fixed under the assumption that the closed loop system remains stable at all times. With a few samples of future reference input data available, the preview action of the adaptive feedforward controller cancels the phase lag caused by the closed loop dynamics and attains the zero phase error tracking performance (i.e., the plant output is in phase with any sinusoidal desired output) asymptotically.
Modularity and Causality in Physical System Modelling
Authors: Hogan N.
Published: July 2009

Decomposition and reassembly of a physical system should not change the form of its describing equations; the physics and mechanics describing each component of a machine remain the same whether the components are separate or assembled into a complete system. In general, the differential equations used to model physical systems do not share this property. This paper considers restrictions on the structure of mathematical models of physical systems which endow the equations with the same modularity as the physical system. It is shown that models based on nonenergic junctions (ideal series and parallel connections) cannot guarantee this property. Generalized energic junction structures are proposed and it is shown that they are sufficient to guarantee modularity.
A Series-Parallel Identifier With Auxiliary Signals
Authors: Baradello C. S. , Neuman C. P.
Published: July 2009

Auxiliary signals which are proportional to the tracking error between the process and identifier outputs are introduced into the series-parallel (SP) identifier [1-2]. The coefficients of these auxiliary signals are updated at each computational cycle. The asymptotic hyperstability of the resulting SP identifier with variable relaxation gains is proved theoretically and demonstrated experimentally. Computational considerations for implementing SP identifiers are noted and the on-line computational requirements of the two SP identifiers are then compared.
Hunting of Evaporators Controlled by a Thermostatic Expansion Valve
Authors: Broersen P. M. T. , van der Jagt M. F. G.
Published: July 2009

Evaporators controlled by a thermostatic expansion valve can exhibit an undesirable oscillating behavior, known as hunting. The equations describing the hunting can be characterized by an open-loop transfer function, the coefficients of which are the physical parameters of a refrigeration system. Several known experimental facts are explained theoretically by means of this transfer function, which also provides a starting point for finding new methods to improve the behavior. A particular improvement was verified experimentally.
Application of Microcomputers to Automatic Weld Quality Control
Authors: Tomizuka M. , Dornfeld D. , Purcell M.
Published: July 2009

The demand for increased productivity of welding operations has led to the expanded use of computer control to allow higher production rates while maintaining weld quality. The charateristics of the gas metal arc welding process and the relationship between welding parameters, the desired output of the welding process, and the automation of the process are discussed. A strategy for two-axis welding torch positioning and velocity control is developed based on preview control techniques. To evaluate the applicability of the proposed control method the motion of heat source along different welding paths is simulated on an analog computer with on-line control of process time constants by an LSI-11 microcomputer. The simulation results show that high quality seam tracking can be accomplished by controlling the torch motion using the proposed method. The method appears to be suitable for on-line control of welding processes.
Sampled-Data Systems, Revisited: Reflections, Recollections, and Reassessments
Authors: Jury E. I.
Published: July 2009

A review of the progress made in sampled-data systems during the last thirty years is presented in this paper. In particular the impact of the discrete theory on the continuous counterpart is mentioned. Additionally, the limiting process of discrete system theory when the discrete interval (or the sampling period) goes to zero, is discussed. Recent emergence of digital signal processing and digital filters as an aftermath of sampled-data systems is brought into focus as well as the technological developments which aided in this new development. The paper concludes with a critical view of the past achievements in this field as well as indications of possible future developments.
Discrete Control Algorithm for a Heat Storage System
Authors: Kulakowski B. T. , Schmidt F. W.
Published: July 2009

The discrete control algorithm of a system incorporating a heat storage unit is presented. This system is required to supply thermal energy so that the given time varying load could be satisfied. A simple linear finite difference approximation of the process dynamics represented by the set of hyperbolic equations provides the basis for the control strategy. No initial knowledge of the values of the process parameters is necessary as the on-line identification procedure is incorporated in the control algorithm. The results of computer simulation indicate that the satisfactory performance of the system can be achieved even with a first order finite difference approximation of the heat storage unit behavior. A microprocessor-based system is recommended for implementation of the control algorithm.
A Sensing Technique for Controlled Intervention in Protective Systems
Authors: Sanathanan C. K. , Warinner D. K. , Tessier J. H.
Published: July 2009

This paper presents a case study of the safety instrumentation for a class of intensive heat-transfer systems that must be protected against severe loss of cooling while preventing premature intervention for momentary loss of cooling. A safety experiment conducted in a test nuclear reactor to simulate abnormal conditions in a prototypic Liquid-Metal-Cooled Fast Breeder Reactor core subassembly is used to illustrate the surveillance technique. The protective action arising from a decision based on loss-of-cooling severity is referred to as controlled intervention. The decision-making process is based on real-time interpretation of measured signals by hard-wire analog methods; the test reactor’s plant-protection system requires a simple and reliable sensing device. The output of a moving-time-average filter (whose input is the coolant-flow-rate measurement signal) is found to be capable of discriminating between insignificant and significant flow disruption and it is therefore used to trigger the decision logic to scram the reactor automatically.
On Free Vibrations With Combined Viscous and Coulomb Damping
Authors: Markho P. H.
Published: July 2009

A closed-form solution of the governing, nonlinear equation for free vibrations of a single-degree-of-freedom system, without stops, under combined viscous and Coulomb damping is first obtained. This is much less involved than forced-response considerations of the same system (with or without stops) the solution of which problem was first obtained by Den Hartog [1]. This note contains the first derivation, as far as the author is aware of, of the equation for the amplitude decay curve (or envelope) for such a system vibrating freely under no-stop conditions. This equation is presented in a form which enables the components of the damping force to be determined from the system’s experimental plot (or record) of displacement versus time.
A Simulation-Based Approach to the Design of Control Systems With Uncertain Parameters
Authors: Auslander D. M. , Spear R. C. , Young G. E.
Published: July 2009

A design method for control systems with uncertain parameters is presented. The method utilizes a generalized sensitivity approach which separates the parameter space into regions which produce a system response that satisfies given design criteria and regions which do not. Nonparametric statistics and confidence limits for the binomial distribution are used to determine degree of parameter sensitivity and to locate regions in the parameter space which maximize the probability of producing a desirable system response. In an example it is shown that a given parameter may have to be known to a lesser degree of uncertainty to be able to specify a satisfactory design.
Modelling and Performance Assessment of an Antenna-Control System
Authors: Burrows C. R.
Published: July 2009

An assessment is made of a surveillance-radar control system designed to provide a sector-search capability and continuous control of antenna speed without unwanted torque-reaction on the supporting mast. These objectives are attained by utilizing regenerative braking, and control is exercised through Perbury CVTs. A detailed analysis of the system is given. The models derived for the Perbury CVTs supplement the qualitative data contained in earlier papers. Some results from a computer simulation are presented. Although the paper is concerned with a particular problem, the analysis of the CVTs, and the concept of using energy transfer to control large inertial loads, are of more general interest.
An Approach, Via Entropy, to the Stability of Random Large-Scale Sampled-Data Systems Under Structural Perturbations
Authors: Jumarie Guy
Published: July 2009

The concept of entropy in information theory is used to investigate the sensitivity and the stability of sampled-data systems in the presence of random perturbations. After a brief background on the definition, the practical meaning and the main properties of the entropy, its relations with asymptotic insensitiveness are exhibited and then some new results on the sensitivity and the stochastic stability of linear and nonlinear multivariable sampled data systems are derived. A new concept of stochastic conditional asymptotic stability is obtained which seems to be of direct application in the analysis of large-scale systems. Sufficient conditions for stability are stated. This approach provides a new look over stochastic stability. In addition, variable transformations act additively on entropy, via Jacobian determinant, and as a result the corresponding calculus is very simple.
Identification of Multi-Input Multi-Output Linear Systems From Frequency Response Data
Authors: Lin P. L. , Wu Y. C.
Published: July 2009

A procedure for identifying a multi-input multi-output linear system from frequency response data is developed. Individual transfer functions from individual input to individual output are identified via the generalized least-squares theory. Orders of the transfer functions are determined by testing the residual. The minimal order multi-input multi-output system is identified based on the formation of a composite system comprising the subsystems associated with all individual outputs followed by decomposition. This is actually the problem of minimal realization involving inexact system parameters.
Performance Analysis and Testing of a Conventional Three-Piece Freight Car Truck Retrofitted to Provide Axle Steering
Authors: Marcotte P. , Caldwell W. N. , List H. A.
Published: July 2009

The paper reviews the performance analysis and test work carried out on a conventional three-piece freight car truck retrofitted with elastomeric elements and cast steel steering arms in order to provide axle steering on curves and improved dynamic stability at higher speeds. A general approach on truck design is presented concerning linear truck dynamic stability and linear/nonlinear steady-state curve negotiation. Results of comparative performance tests are given, including the measurement of interaxle stiffnesses and the measurement of forces and angles of attack in curves, for both the conventional and the modified trucks. Comments are given on the economic impact that the retrofitted steering truck is expected to have on railway operations.
A Steering Control System to Minimize Propulsion Losses of High-Speed Containerships—Part II: Controller Design
Authors: Reid R. E. , Moore J. W.
Published: July 2009

An approach to design of steering controls for high-speed containerships to minimize propulsion losses is described. It involves time domain modeling and simulation, frequency domain analysis, and control structure investigation. A design process based on the use of linear modern and classical control techniques with locally linear models to minimize propulsion losses at important design conditions on the ship’s operating envelope is discussed. An adaptive controller to provide envelope-wide control in the face of changing environmental conditions and ship characteristics is described. Results from simulations and full-scale sea tests are summarized. On the basis of these preliminary results it appears that the adaptive controller works well under different speed and weather conditions and offers the potential for a reduction in propulsion losses over an existing PID autopilot.
Principal Developments in the Adaptive Control of Machine Tools
Authors: Ulsoy A. Galip , Koren Yoram , Rasmussen Fred
Published: July 2009

Although adaptive control (AC) systems for machine tools have a tremendous potential for improving productivity in manufacturing, their acceptance by industry has been slow. This paper identifies the major research and development areas for AC machine tools, and summarizes the principal developments of the last two decades. Current research at The University of Michigan, which is aimed at the development of stable yet high performance AC systems for turning and milling, is also described.
Minimization of Energy Storage Requirements for Internal Combustion Engine Hybrid Vehicles
Authors: Beachley N. H. , Anscomb C. , Burrows C. R.
Published: July 2009

The use of energy storage in an automobile provides two important fuel-saving advantages: first the engine can be run at or close to its condition of maximum efficiency, and secondly the energy of braking can be recovered regeneratively. This paper examines how these factors are linked to the size of the energy storage unit and describes a control policy which has the purpose of minimizing the capacity whilst retaining the fuel-saving benefits. Both flywheel and accumulator storage units are considered; results are obtained for three standard test cycles. Some preliminary attempts are made to assess the effect of road gradient. It is concluded that a capacity of the order of 0.15 to 0.20 MJ for a 1360 kg automobile would provide most of the fuel-saving benefits for typical driving patterns where grade is not an important consideration.
The Application of Sensitivity Analysis to Electrohydraulic Position Control Servos
Authors: Vilenius M. J.
Published: July 2009

Sensitivity analysis is applied to an investigation of the influences of design parameters on the dynamics of electrohydraulic position control servos. A sensitivity model suitable for certain nonlinear dynamic systems is introduced in general form. State equations may have nonlinearities that are continuously twice differentiable with respect to the state vector and parameter vector and nonlinearities such as deadband. As an example parameter influences on a servo system typical in the sawmill industry are considered.
An Algebraically Derived Nonlinear Control Theory
Authors: Fish A. J. , Jordan D.
Published: July 2009

This paper presents a control theory, for a large class of nonlinear systems, including analog, digital, and hybrid systems. The control theory is developed from a new system model that can be used to model nonlinear systems that cannot be modeled with the state space equations.
A Linear Algebra Approach to the Analysis of Rigid Body Velocity From Position and Velocity Data
Authors: Laub A. J. , Shiflett G. R.
Published: July 2009

The instantaneous velocity of a rigid body in space is characterized by an angular and translational velocity. By representing the angular velocity as a matrix and the translational component as a vector the velocity of any point in the rigid body may be found if the position of the point and the parameters of the angular and translational velocities are known. Alternatively, the parameters of the rigid body velocity may be determined if the velocity and position of three points fixed in the body are known. In this paper, a new matrix-theory-based method is derived for determining the instantaneous velocity parameters of rigid body motion in terms of the velocity and position of three noncollinear points fixed in the body. The method is shown to possess certain advantages over traditional vectoral solutions to the same problem.
Feedback Control and Simulation of a Wheelchair
Authors: Shung J. B. , Tomizuka M. , Auslander D. M. , Stout G.
Published: July 2009

This paper presents a wheelchair velocity feedback controller intended to reduce the control demands on a wheelchair driver in outdoor driving and in low speed maneuvering. A dynamic model of a wheelchair and its motor control circuitry is used in the controller design. A computer simulation study is conducted for the controller. The results indicate that the velocity feedback controller should make the chair easier to drive under varying road conditions.
Design of Hydraulic Servovalve for Maximum Pressure Sensitivity
Authors: LeQuoc S.
Published: July 2009

The performance of a hydraulic servomechanism depends largely upon the servovalve characteristics which in turn are determined by various physical parameters such as spool land width, radial clearance etc... The work described in this paper is concerned with the design of hydraulic spool valve for a maximum pressure sensitivity in a no load flow application. It has been demonstrated that this condition is achieved by having an underlap equal to the radial clearance. The results are experimentally verified and the effects of rounded corners of metering lands on the pressure sensitivity curves are discussed.
A Design Methodology for Nonlinear Systems Containing Parameter Uncertainty
Authors: Young G. E. , Auslander D. M.
Published: July 2009

A design methodology capable of dealing with nonlinear systems containing parameter uncertainty is presented. A generalized sensitivity analysis is incorporated which utilizes sampling of the parameter space and statistical inference. For a system with j adjustable and k nonadjustable parameters, this methodology (which includes an adaptive random search strategy) is used to determine the combination of j adjustable parameter values which maximizes the probability of the performance indices simultaneously satisfying design criteria given the uncertainty in the k nonadjustable parameters.
A Control Strategy for Computer Numerical Control Machine Exhibiting Precision and Rapidity
Authors: Doraiswami R. , Gulliver A.
Published: July 2009

A digital controller for a closed loop computer numerical control machine demonstrating precision and rapidity in machining a given contour is proposed. The digital controller contains a digital filter which generates a copy of the reference input and the load torque disturbance signals. The reference inputs are both analytic and piecewise analytic signals. The closed loop system is stabilized using a digital stabilizer. The mathematical model of the process considers the lead-screw dynamics and the axial stiffness. Hybrid simulation of machining is used to compare conventional with proposed controllers. The effects of nonlinearities, noise, and parameter variation are considered in simulation.
Active Control of Robot Structure Deflections
Authors: Zalucky A. , Hardt D. E.
Published: July 2009

The characteristic beam-like structure of most robots leads to significant bending deflections, which in turn lead to poor endpoint positioning accuracy. One solution is to actively counteract this bending using a “straightness servo.” In this paper, such a system is proposed comprising two parallel beams, one to act as the manipulator link and one to carry only the bending loads. These beams are clamped together at one end and joined at the other by an hydraulic actuator. A single variable straightness control system is presented and analyzed. Simulations based upon a realistically sized prototype indicate that attenuation of force disturbances (compliance reduction) to less than 0.006 cm/kN (e.g., 0.001 in./100 lb.) is possible over a 10 Hz bandwidth. Also, system stability can be maintained even when additional mass (which changes the system parameters) is placed at the endpoint. There results are verified by experiments on a full size prototype. Greater improvements in system bandwidth will require state variable control because of the high dynamic order of the structure.
Vibration Control in Rotating or Translating Elastic Systems
Authors: Ulsoy A. Galip
Published: July 2009

The reduction of vibration in rotating or translating elastic systems (e.g., shafts, circular saws, belts, handsaws) is an important engineering problem. This paper presents the characteristics of rotating or translating elastic system vibration problems which are significant for the design of active controllers. The effect of the rotation or translation velocity on the controller design, and the effects of observation and control spillover are discussed. Simulation results for two example problems, a rotating cantilever shaft and an axially moving string, are used to illustrate the design and performance of active vibration controllers for rotating or translating elastic systems.
Temperature Independent Fluidic Resistive Circuits and Concepts
Authors: Drzewiecki T. M.
Published: July 2009

This paper discusses series and parallel topologies of orifices and capillaries as fluidic resistors and the way that they relate to temperature sensitivity and temperature compensation. Examination of a laminar flow nozzle, as typically found in a laminar proportional amplifier (LPA), shows that it may be represented by a parallel combination of an orifice and a capillary. As a result a nozzle has inherent temperature insensitive properties that allow temperature independent operation of such laminar fluidic devices as pressure controlled oscillators. It is shown that one may design a constant resistance, within ±0.1 percent, for changes in environmental temperature of ±20°C when air is the working fluid.
Nonlinear Control of Mismatched Uncertain Linear Systems and Application to Control of Aircraft
Authors: Singh S. N. , Coelho Antoˆnio A. R.
Published: July 2009

This paper describes an approach to control of nonzero set points of uncertain linear systems based on the theory of ultimate boundedness. We derive a nonlinear control which guarantees that every system response is ultimately bounded within a certain neighborhood of the desired nonzero set point. Analytical expressions for the bounds on variations in parameters for ultimate boundedness are obtained. These results are applied to control of a VTOL aircraft whose time-varying parameters are uncertain. Unlike previous works, arbitrary and fast variations in aircraft parameters are allowed. It is shown that the nonlinear controller is effective for larger variation in parameters than the reduced linear controller. Digital simulation results show that the aircraft can be precisely maneuvered in spite of uncertain parameter variations.
An Analysis of Pulse Control for Simple Mechanical Systems
Authors: Prucz Z. , Soong T. T. , Reinhorn A.
Published: July 2009

An efficient pulse control method for insuring safety of simple mechanical systems is developed and its sensitivity to the excitation frequency content and to various control parameters is studied. The control algorithm, consisting of applying pulse forces in a feedback fashion, is designed to insure that maximum system response is limited to safe values at all times. It is shown that the proposed algorithm is simple to implement and is efficient in controlling peak response in terms of on-line computation and pulse energy required. The technique is illustrated and analyzed for a single-degree-of-freedom linear system.
Dynamics of a Nonlinear Oscillator With Feedback Control I: Local Analysis
Authors: Holmes P.
Published: July 2009

We study stability and bifurcations of solutions of a single degree of freedom structural system with nonlinear stiffness, subject to linear feedback control. The controller dynamics is modelled by a first order differential equation, so that the full system is of third order. In this paper we consider local bifurcations: solutions branching from equilibria as various parameters (damping, gain, etc.) are varied. Using two different nonlinear stiffness functions, we show that interactions between steady and periodic modes of instability leads to complicated dynamical behavior near the boundaries of the “stable” region of parameter space.
Controller Tuning Based on Stochastic Control Theory
Authors: Chou Sidney
Published: July 2009

A practical controller tuning method is proposed for selecting controller gains in the face of design difficulties such as poor repeatability, long delay, nonlinearity, conflicting control objectives, model inaccuracy, and system complexity. Unlike many adaptive schemes striving to acquire knowledge about the system being controlled, the proposed approach is aimed at designing nonadaptive, or at best, gain scheduling controllers in a quantitative, systematic way while meeting design specifications.
Stability Optimization of Multi-Axle Railway Vehicles Possessing Perfect Steering
Authors: Wickens A. H.
Published: July 2009

The general form of the equations of motion of multi-axle railway vehicles are used to establish the conditions which the elastic stiffness matrix (which describes the nature and configuration of the suspension elements connecting the wheelsets) must satisfy in order to achieve perfect steering on curves, an adequate margin of stability and optimal response to cant deficiency. These conditions are illustrated by application to the most general form of symmetric three-axle vehicle and it is shown that an adequate margin of stability can be obtained for an optimized set of parameters which allows perfect linear curving. The class of configurations studied allows for unequal wheelset conicities and interwheelset assymmetry within the assumption of overall vehicle symmetry.
Applications of Damped Least-Squares Methods to Resolved-Rate and Resolved-Acceleration Control of Manipulators
Authors: Wampler C. W. , Leifer L. J.
Published: July 2009

Resolved-rate and resolved-acceleration controllers have been proposed for manipulators whose trajectories are determined by real-time sensory feedback. For redundant manipulators, these controllers have been generalized using the pseudoinverse of the manipulator Jacobian. However, near singular configurations, these controllers fail in that they require infeasibly large joint speeds. A damped least-squares reformation of the problem gives approximate inverse kinematic solutions that are free of singularities. Away from singularities the new controllers closely approximate their conventional counterparts; near singular configurations the new controllers remain well-behaved, although the rate of convergence decreases. This paper defines the new controllers and proves their stability. Some aspects of the behavior of the new resolved-rate controller are illustrated in simulations.
Implementation of Adaptive Techniques for Motion Control of Robotic Manipulators
Authors: Tomizuka M. , Horowitz R. , Anwar G. , Jia Y. L.
Published: July 2009

This paper is concerned with the digital implementation and experimental evaluation of two adaptive controllers for robotic manipulators. The first is a continuous time model reference adaptive controller, and the second is a discrete time adaptive controller. The primary purpose of these adaptive controllers is to compensate for inertial variations due to changes in configuration and payload, as well as disturbances, such as Coulomb friction and/or gravitational forces. Experimental results are obtained from a laboratory test stand, which emulates an one-axis direct drive robot arm with variable inertia, as well as a Toshiba TSR-500V industrial robot. Experimental results from the test stand indicate that these adaptive control schemes are promising for the control of direct drive robot arms. Friction forces arising from the harmonic gear of the Toshiba robot were detrimental if not properly compensated. Because of a high gearing ratio, the advantage of adaptive control for the Toshiba arm could be shown only by detuning the controller.