bluuebunny/crossref_metadata_2025 huggingface dataset:
Randomized Trial of a Portable, Self-administered Decision Aid for Postmenopausal Women Considering Long-term Preventive Hormone Therapy
Authors: O'Connor Annette M. , Tugwell Peter , Wells George A. , Elmslie Tom , Jolly Elaine , Hollingworth Gary , Mcpherson Ruth , Drake Elizabeth , Hopman Wilma , Mackenzie Thomas
Published: March 2007

Although practice guidelines suggest that postmenopausal women learn about the benefits and nsks and consider their values when deciding about hormone therapy, the optimal decision-support method has not been established. In a randomized controlled trial, the authors compared the efficacy of a general educational pamphlet with that of a tailored decision aid. The pamphlet briefly summarized benefits, risks, and likely beneficiaries in general terms. The decision aid, delivered via booklet and audiotape, provided: detailed benefits and risks using functional terms and probabilities tailored to clinical risk; and steps for considering the issue in a woman's own situation, including a value-clarification exercise. Compared with the pamphlet group, the decision-aid group had statistically significant (p < 0.05) improvements in terms of realistic personal expectations of the benefits and nsks, decisional conflict, and perceived acceptability of the intervention. Levels of general knowledge about the main benefits and nsks were comparable for the two interventions It is concluded that tailored decision aids prepare women for decision making better than do general pamphlets. Key words: decision making; choice behavior; informed consent; decision-support techniques; woman education; woman participation; health education; consumer satisfaction; hormone replacement therapy; menopause. (Med Decis Making 1998;18:295-303)
The Danger of Applying Group-level Utilities in Decision Analyses of the Treatment of Localized Prostate Cancer in Individual Patients
Authors: Cowen Mark E. , Miles Brian J. , Cahill Daniel F. , Giesler R. Brian , Beck J. Robert , Kattan Michael W.
Published: March 2007

The optimal management strategy for men who have localized prostate cancer remains controversial. This study examines the extent to which suggested treatment based on the perspective of a group or society agrees with that derived from individual patients' preferences. A previously published decision analysis for localized prostate cancer was used to suggest the treatment that maximized quality-adjusted life expectancy. Two treatment recommendations were obtained for each patient: the first (group-level) was derived using the mean utilities of the cohort; the second (individual-level) used his own set of utilities. Group-level utilities misrepresented 25-48% of individuals' pref erences depending on the grade of tumor modeled. The best kappa measure achieved between group and individual preferences was 0.11. The average quality-adjusted life years lost due to misrepresentation of preference was as high as 1.7 quality-adjusted life years. Use of aggregated utilities in a group-level decision analysis can ignore the substantial variability at the individual level. Caution is needed when applying a group- level recommendation to the treatment of localized prostate cancer in an individual patient. Key words: decision analysis; utility assessment; prostate cancer; patient pref erences. (Med Decis Making 1998;18:376-380)
Problems with Interval Estimates of the Incremental Cost—Effectiveness Ratio
Authors: Heitjan Daniel F. , Moskowitz Alan J. , Whang William
Published: March 2007

The defining feature of a confidence interval is that it has a fixed minimum probability of covering the true value of the parameter being estimated, whatever the value of the parameter. The authors demonstrate by simulation that some recently proposed meth ods for interval estimation of the incremental cost—effectiveness ratio (ICER) either do not satisfy this definition or have other problems that limit their usefulness in applica tions. The problems are most prominent when the ICER is large and the true effec tiveness difference is small relative to its standard error. A modification of the percentile bootstrap confidence interval that involves a reordering of the sample space provides a partial solution of the problem. Key words: bootstrap; clinical trials; confidence inter vals ; cost—effectiveness ratios; Fieller's method; Taylor series. (Med Decis Making 1999;19:9-15)
Measuring Patient Preferences by Willingness to Pay to Avoid
Authors: Sorum Paul Clay
Published: March 2007

The aim of this study was to evaluate willingness to pay (WTP) to avoid as a method of eliciting relative values for use in expected-value (EV) decision making. Parents' preferences for the events and outcomes associated with acute otitis media (AOM) and its treatment were quantified by means of a questionnaire asking how much they would be willing to pay to avoid them. Their responses were then used to calculate the EVs of treating or not treating presumed AOM with antibiotics. The advantages of the WTP method were its simplicity, its analogy with everyday financial transactions, its explicit recognition of illness and its management as involving decreases in value, and its face validity. The disadvantages included the need to use another method (the standard gamble) to derive a value for death and the wide ranges and the poor test—retest reliability of individual parents' responses. Nonetheless, median WTP val ues and their ranges may prove useful in defining for physicians and policymakers the parameters of their practical management decisions. In the case of AOM, the EV of treating with antibiotics was, for the aggregate sample and for most individual parents, robustly superior because of parents' desire to avoid any increased risk of their chil dren's death. Key words: willingness-to-pay; expected value decision making; patient preferences; acute otitis media; antibiotic treatment. (Med Decis Making 1999;19: 27-37)
Computing Population-based Estimates of Health-adjusted Life Expectancy
Authors: Rosenberg Marjorie A. , Fryback Dennis G. , Lawrence William F.
Published: March 2007

Observed health-adjusted life expectancy (HALE) is an indicator of population health. There are a number of ways to compute HALE for a community. The authors surveyed several methods and demonstrate resulting variation in the estimates of HALE. Quality of well-being (QWB) measures from 1,430 participants in the Beaver Dam Health Out comes Study are taken as weights. Actuarial life-table methods using community mor tality data, State of Wisconsin census data from two time frames, and U.S. census data are used with the QWB to estimate HALE. Measurement of community population health using HALE computations can be completed with national, regional, or local data. Community-level estimates may not be well approximated using large-scale mor tality experience. A Bayesian method is developed combining the local data with re gional data. The Bayesian method creates a smooth set of rates, retains the local flavor of the community, and gives a measure of variability of the estimated HALE. Key words: quality-of-life measures; Bayesian methodology; Gibbs sampling. (Med Decis Making 1999;19:90-97)
A Survey of Gynecologists' Attitudes Regarding Decision Making in the Management of Non-cancerous Conditions That Frequently Result in Hysterectomy
Authors: Dolan James G. , Howard Fred M.
Published: March 2007

Objective. To explore attitudes of practicing gynecologists regarding making treatment decisions for patients with benign uterine conditions frequently treated with hysterec tomy. Design. Mailed survey. Participants. 66 gynecologists practicing in the Greater Rochester, New York, area. Interventions. After reading brief vignettes, respondents indicated how they would treat patients with chronic pelvic pain, uterine leiomyomas, and abnormal uterine bleeding, and rated the importance of 24 considerations in mak ing their treatment decisions on a 1-to-5 scale ranging from not important to extremely important. Results. Fourteen considerations (58%) had group mean importance ratings higher than 3. Exploratory factor analysis identified four factors that accounted for 96% of the variance. Respondent gender, practice type, graduation from a U.S. vs a non- U.S. medical school, and opinion regarding roles of doctor and patient in making treat ment decisions were associated with significant differences in factor scores. Conclu sions. Gynecologists' attitudes toward hysterectomy decisions are complex, multifactorial, and variable. Depending on the extent to which these attitudes affect treatment decisions, differences among gynecologists in their clinical decision making processes could account for a substantial amount of the regional variability in hyster ectomy use. Key words: decision making; hysterectomy, physician-patient relation ship. (Med Decis Making 1999;19:186-192)
Evaluation of a Shared Decision Making Program for Women Suspected to Have a Genetic Predisposition to Breast Cancer
Authors: Stalmeier Peep F.M. , Unic Ivana J. , Verhoef Lia C.G. , Van Daal Willem A.J.
Published: March 2007

Background. Women suspected to have a genetic predisposition to breast cancer face the difficult choice between regular breast cancer screening and prophylactic mastec tomy. The authors developed a shared decision making program (SDMP) to support this decision. Objectives. To evaluate the SDMP in terms of practicality, beneficial effects, and patient satisfaction. Design. A one-group pretest-posttest design was used. Measures. Decision uncertainty, decision burden, subjective knowledge, and risk comprehension were assessed before and after the SDMP. Additional measures were obtained for concepts related to breast cancer concern, desire to participate in the program, satisfaction, program acceptability, and emotional reaction to the program information. Results. Seventy-two women, most of whom were awaiting the genetic test results, participated. Decision uncertainty (effect size d = 0.37) and decision bur den (d= 0.41) were reduced by the SDMP. Subjective knowledge (averaged d= 0.94) and risk comprehension were improved. The women were satisfied with the SDMP and found its rationale acceptable. Women who had strong emotional reactions to the information benefited less from the SDMP, whereas women with strong desires to participate in the decision benefited more. Conclusions. There is a need to give pa tients more information, especially about prophylactic mastectomy and among gene carriers. Beneficial effects were observed irrespective of whether genetic status was known, suggesting that information concerning treatment options should be made available as soon as DNA testing begins. The better psychological outcomes of women with stronger desires to participate may arise because the desire to participate is char acteristic of emotional stability. Key words: shared decision making; breast cancer; genetic predisposition; patient participation; patient satisfaction. (Med Decis Making 1999; 19:230-241)
Bayesian Approaches to Meta-analysi of ROC Curves
Authors: Hellmich Martin , Abrams Keith R. , Sutton Alex J.
Published: March 2007

A comparative review of important classic and Bayesian approaches to fixed-effects and random-effects meta-analysis of binormal ROC curves and areas underneath them is presented. The ROC analyses results of seven evaluation studies concerning the dexamethasone suppression test provide the basis for a worked example. Particular attention is given to fully Bayesian inference, a novelty in the ROC context, based on Gibbs samples from posterior distributions of hierarchical model parameters and re lated quantities. Fully Bayesian meta-analysis may properly account for the uncertainty associated with the model parameters, possibly incorporating prior knowledge and beliefs, and allows clinically intuitive predictions of unobserved study effects via cal culation of posterior predictive densities. The effects of various different prior specifi cations (six noninformative as well as one informative) on the posterior estimates are investigated (sensitivity-analysis). Recommendations and suggestions for further re search are made. Computer code for the more advanced methods may either be downloaded via the Internet or be found elsewhere. Key words : Bayesian methods; random effects; meta-analysis; ROC curve; diagnostic test; hierarchical models; Mar kov-chain Monte Carlo technique; Gibbs sampling; maximum likelihood; method of moments. (Med Decis Making 1999; 19:252-264)
Effects on Preferences of Violations of Procedural Invariance
Authors: Lenert Leslie A. , Treadwell Jonathan R.
Published: March 2007

Background. In studies of health preferences, utilities for hypothetical health states cannot always be successfully measured. One marker for unsuccessful measurement is violation of "procedural invariance": when the ranking of two health states varies across assessment procedures. Using preference values based on unsuccessful mea surement may result in misinterpretation of patients' attitudes about health. Objective. The authors sought to determine whether people who violated procedural invariance had different preferences than people who satisfied it. Methods. They performed sec ondary analyses of three completed studies that used the same two assessment pro cedures, identifying participants who violated procedural invariance and comparing the mean standard gamble (SG) and visual analog scale (VAS) scores of violators and satisfiers. Participants. Experiment 1, 30 healthy volunteers and 30 patients with car diac arrhythmias; expenment 2, 139 patients with depressive illness; experiment 3, 98 family members of patients with schizophrenia. Results. Rates of violation of proce dural invariance ranged from 16% to 32%. Violation of procedural invariance was not associated with age, education level, race, or gender. Subjects with violations of pro cedural invariance had, in general, less ability to discriminate among states and less reliable VAS and SG measurements, and sometimes had different mean SG and VAS values. Conclusions. Violation of procedural invariance of preferences across scaling methods may be a signal for failure of the measurement process. Researchers should test for procedural invariance and consider reporting data separately for satisfiers and violators. Key words: utility; standard gamble; visual analog scale; cost-effectiveness analysis; decision analysis; computers; preferences. (Med Decis Making 1999;19: 473-481)
Fast Nonlinear Control with Arbitrary Pole-Placement for Industrial Robots and Manipulators
Authors: Freund E.
Published: March 2007

Models of industrial robots are characterized by highly nonlinear equations with nonlinear couplings between the variables of motion. In this paper, three nonlinear methods are presented, two of which are direct design procedures for industrial robots. These direct nonlinear methods are based on a suitable partition of the dynamic equation of the industrial robot and provide directly applicable, explicit control laws for each drive. The design procedures presented greatly simplify the derivation of the algorithm for computer-controlled industrial robots. The methods are applied to two different types of industrial robots.
AML: A Manufacturing Language
Authors: Taylor R.H. , Summers P.D. , Meyer J.M.
Published: March 2007

AML, A Maufacturing Language, was designed to be a well-structured, semantically powerful interactive language for robot programming. In this paper, we identify the de sign objectives for such a language and give a technical description of AML. Important features are described and illustrated through representative examples of robot appli cations programming.
Recognizing and Locating Partially Visible Objects: The Local-Feature-Focus Method
Authors: Bolles Robert C. , Cain Ronald A.
Published: March 2007

A new method of locating partially visible two-dimensional objects is presented. The method is used to locate complex industrial parts that may contain several occurrences of local features, such as holes and corners. The matching process utilizes clusters of mutually consistent features to hypothesize objects and also uses templates of objects to verify these hypotheses. The technique is fast because it concentrates on key features that are automatically se lected on the basis of a detailed analysis of computer- aided design (CAD) models of the objects. The automatic analysis applies general-purpose routines for building and analyzing representations of clusters of local features that could be used in procedures to select features for other lo cational strategies. These routines include algorithms for computing the rotational and mirror symmetries of objects in terms of their local features.
Configuration Design of the Adaptive Suspension Vehicle
Authors: Waldron Kenneth J. , Vohnout Vincent J. , Pery Arrie , McGhee Robert B.
Published: March 2007

The selection of vehicle and leg configuration and of power transmission and actuation system configuration for the adaptive suspension vehicle ( ASV) are discussed. The ASV will be a proof-of-concept prototype of a proposed class of transportation vehicles for use in terrain that is not passable for conventional vehicles. It uses a legged locomotion princi ple. The machine will not be an autonomous "robot, " in the sense that it will carry an operator. It will, however, have a very high level of machine intelligence and environmental sensing capability. Much of the technology involved is unique and has potential for application to future robot systems. In this paper, major aspects of the vehicle and leg geometry, the on-board processing configuration, and the hydrostatic power transmission system are discussed.
Experiments in Balance with a 3D One-Legged Hopping Machine
Authors: Raibert Marc H. , Brown H. Benjamin , Chepponis Michael
Published: March 2007

In order to explore the balance in legged locomotion, we are studying systems that hop and run on one springy leg. Pre vious work has shown that relatively simple algorithms can achieve balance on one leg for the special case of a system that is constrained mechanically to operate in a plane ( Rai bert, in press; Raibert and Brown, in press). Here we general ize the approach to a three-dimensional ( 3D) one-legged machine that runs and balances on an open floor without physical support. We decompose control of the machine into three separate parts: one part that controls forward running velocity, one part that controls attitude of the body, and a third part that controls hopping height. Experiments with a physical 3D one-legged hopping machine showed that this control scheme, while simple to implement, is powerful enough to permit hopping in place, running at a desired rate, and travel along a simple path. These algorithms that control locomotion in 3D are direct generalizations of those in 2D, with surprisingly little additional complication.
Initial Experiments on the End-Point Control of a Flexible One-Link Robot
Authors: Cannon Robert H. , Schmitz Eric
Published: March 2007

It has been known for some time ( Gevarter 1970) that if a flexible structure is controlled by locating every sensor exactly at the actuator it will control, then stable operation is easy to achieve. Nearly all commercial robots are controlled in this way, for this reason. So are most flexible spacecraft.

Conversely, when one attempts to control a flexible struc ture by applying control torques at one end that are based on a sensor at the other end, the problem of achieving stability is severe. Solving it is an essential step for better control in space: the space-shuttle arm is a cogent example. The next generation of industrial robots will also need such control capability, for they will need to be much lighter in weight ( to achieve quick response with modest energy), and they will need to achieve greater precision by employing end-point sensing.

A set of experiments has been constructed to demonstrate control strategies for a single-link, very flexible manipulator, where the position of one end is to be sensed and precisely positioned by torquing at the other end. The objective of this first set of experiments is to uncover and solve problems related to the control of very flexible manipulators where sen sors are not colocated with the actuator. The experimental arrangement described here is also a test bed for new designs for flexible-structure controllers, designs that use insensitive, reduced-order control and adaptive control methods, for example. This paper describes the experimental arrangement, model identification, control design, and first experimental results.

Some interesting results are the following. First, good stability can be achieved for such noncolocated systems, and reponse can be achieved that is effectively three times faster than the first natural cantilever period of the system: but a good model of the system dynamics and rather sophisticated control algorithms are essential to doing so. Even then, the system will always be conditionally stable. In addition to the tip sensor, a colocated rate sensor and nearly colocated strain gauges have been found to be very useful for achieving good closed-loop performance, that is, high gain and high band width. Second, there is an ultimate physical limit to achiev able response time, namely, the time required for a wave to travel the length of the member. Well-designed controllers can approach this limit. Third, the use of end-point sensing makes less critical the elaborate dynamic conditioning of position-command signals— "model-following " differentia tors, feed-forward, and the like—such as are typically needed in present-generation robots that use "dead reckoning" in lieu of end-point sensing. With end-point sensing, feedback alone ( suitably conditioned) is sufficient to whip the tip to the commanded position and hold it there precisely. Even more important, a shift in, for example, workpiece with respect to robot base, no longer produces an error.
On-Line Polynomial Trajectories for Robot Manipulators
Authors: Chand Sujeet , Doty Keith L.
Published: March 2007

Robot motion is commonly specified as a Cartesian trajectory of its end-effector. For executing the end-effector trajectory on-line, a look-ahead of a few points on the trajectory is used to generate the joint trajectories. This paper describes the construction of on-line cubic spline joint trajectories,for a limited-point look-ahead on a specified end-effector trajectory, not necessarily Cartesian. An analytical derivation for the ideal number of look-ahead points on the end-effector trajectory_for cubic spline interpolation is given. Experimental and simulation results of the on-line spline interpolation schemes show improved end-effector path tracking and smooth motion for a wide range of sampling rates on the effector trajectory.
A New Actuator of a Joint Mechanism Using TiNi Alloy Wire
Authors: Kuribayashi Katsutoshi
Published: March 2007

A new actuator of a joint mechanism is proposed, composed of two TiNi alloy wires.

First, the static and dynamic properties of the TiNi alloy wire that were not known are analyzed. Then the mathemati cal model of the actuator is induced. Next, the control sys tems of the actuator are synthesized by pulse width modu lated (PWM) controllers, and the mathematical models of the control systems are then obtained. Finally, the experiments of the position and force control systems of the actuator are carried out. It is proved that the theoretical models obtained are valid and that the position and force controls of this actuator are possible.

Moreover, the unknown characteristics of the other well- known type of actuator composed of a TiNi alloy wire and an ordinary spring are also analyzed by the above procedure. The mathematical models are presented.
ET: A Wrist Mechanism without Singular Positions
Authors: Trevelyan James P. , Kovesi Peter D. , Ong Michael , Elford David
Published: March 2007

A robot that responds to sensed changes in its environment needs well-conditioned kinematics to maintain adequate dynamic performance and to avoid practical difficulties with flexible cables and actuator limits. We show that it is possi ble to design a wrist mechanism with a large angular work space without any singularities. Although the singularities exist, they are allocated to a single wrist position outside the mechanical limits. The kinematics of the mechanism show that, although the degeneracy cone is larger than for the other wrist mechanisms, it is also largely outside the me chanical limits. Some extensions of the established concept of singularity cones are required. We introduce the concept of "least favorable reorientation " to define the usable workspace of the wrist. Dynamic performance specifications for the wrist are framed in terms of desired single actuator responses under given worst-case situations. Lightweight linear hydrau lic actuators have been used; however, the design can be rearranged to use precision electric drives. The wrist will be used in a new research robot for shearing sheep.
Optimization of Mechanisms for Force Generation by Using Pulleys and Spring
Authors: Okada Tokuji
Published: March 2007

A link mechanism is proposed for force generation by using pulleys and springs (FGPS) based on a scissors structure having two arms, which are effective in energy saving, simpli fication, and miniaturization of a total system of force gener ation.

The relationship between the motion of the mechanism and its output force is analyzed for optimization of structure and dimensions. For optimization of pulley shapes, analyti cal and approximate methods are discussed. Experimental results show that eccentric noncircular pulleys are more effective than circular pulleys in producing a force sufficiently accurate to satisfy conditional relations between the force and the displacement of the mechanism. The mechanism is useful in fulfilling various kinds offorce versus displacement characteristics requirements.
Real-Time Obstacle Avoidance for Manipulators and Mobile Robots
Authors: Khatib Oussama
Published: March 2007

This paper presents a unique real-time obstacle avoidance approach for manipulators and mobile robots based on the artificial potential field concept. Collision avoidance, tradi tionally considered a high level planning problem, can be effectively distributed between different levels of control, al lowing real-time robot operations in a complex environment. This method has been extended to moving obstacles by using a time-varying artificial patential field. We have applied this obstacle avoidance scheme to robot arm mechanisms and have used a new approach to the general problem of real-time manipulator control. We reformulated the manipulator con trol problem as direct control of manipulator motion in oper ational space—the space in which the task is originally described—rather than as control of the task's corresponding joint space motion obtained only after geometric and kine matic transformation. Outside the obstacles' regions of influ ence, we caused the end effector to move in a straight line with an upper speed limit. The artificial potential field ap proach has been extended to collision avoidance for all ma nipulator links. In addition, a joint space artificial potential field is used to satisfy the manipulator internal joint con straints. This method has been implemented in the COSMOS system for a PUMA 560 robot. Real-time collision avoidance demonstrations on moving obstacles have been performed by using visual sensing.
Mapping the Manipulator Workspace Using Interactive Computer Graphics
Authors: Kumar A. , Patel Mayank S.
Published: March 2007

This paper describes an algorithm to map the workspace of a generalized manipulator on computer graphics. A workspace that can be simulated, displayed, and manipulated in real time on computer graphics is a very useful and efficient tool for the analysis, design, and motion planning of a manipula tor. The algorithm is developed for generalized manipulators with constrained revolute and prismatic joints. Workspace characteristics such as size, shape, and presence of holes and voids are investigated. We have tested the algorithm and have concluded that it is computationally feasible and effec tive in mapping the manipulator's workspace on interactive computer graphics.
Type Selection of Robot and Gripper Kinematic Topology Using Expert Systems
Authors: Erdman Arthur G. , Thompson Thomas , Riley Donald R.
Published: March 2007

Robots are used for many different applications including underwater recovery, welding, inspection, pick-and-place operations, space exploration, and assembly. Each task im parts different functional demands on the robot topology including the gripper. An improper choice of the basic kine matic chain may demand sophisticated control algorithms to undo poor type selection.

This paper suggests techniques of type synthesis based on graph theory and expert systems that will aid in proper kine matic topology. This new area of kinematic research has high potential for aiding the robot designer.
Friction, Stability and the Design of Robotic Fingers
Authors: Cutkosky Mark R. , Wright Paul K.
Published: March 2007

For practical reasons, compliant materials are often used on the gripping surfaces of robotic hands. Such materials are not well described by the Coulomb friction law or by simple point-contact or line-contact kinematics. In this paper, a shearing model is used to describe the contact friction. Models ofpointed, curved, flat, soft, and soft-curved fingertips are then developed and compared in terms of their contribu tion to the stiffness and stability of a simple grasp. There is a spectrum of contact conditions defined by the fingertip radius and contact area relative to the object size. This spectrum provides insights for designing and controlling robotic fingers.
Optimal Redundancy Control of Robot Manipulators
Authors: Nakamura Yoshihiko , Hanafusa Hideo
Published: March 2007

This paper discusses the optimal redundancy control problem of robot manipulators. The redundancy control problem has mostly been discussed in the framework of instantaneously optimal control. In this paper, the globally optimal redun dancy control problem is solved strictly by using Pontryagin's maximum principle. According to the proposed method, the optimal trajectory is necessarily obtained if it evists. If only kinematics is considered, the optimal problem is reduced to minimal value searching in a space of as many dimensions as the degrees of redundancy. If dynamics is also taken into consideration, the optimal problem is reduced to minimum value searching in a space of twice as many dimensions as the degrees of redundancy.
Fusion of Multisensor Data
Authors: Richardson John M. , Marsh Kenneth A.
Published: March 2007

This paper treats two parts of the methodology of the fusion of multisensor data: conceptual and applied. In the concep tual part, we treat several basic questions including the fu sionability of various kinds of signals derived from the differ ent sets of raw data associated with separate sensor systems. We require that each derived signal has stand-alone signifi cance. We also derive some general results pertaining to the desirability of augmenting the set of measurements. In the applied part, the general methodology established above is employed in a problem in robotic acquisition involving the determination of the geometry (i.e., the elevation function) of an object resting upon a flat surface. In the model, two types of measurements are assumed: (1) a single acoustical pulse- echo scattering measurement in which the incident wave propagates downward, and (2) a set of optical measurements involving a downward-looking TV camera imaging the object under sequentially pulsed light sources. In the second type, the raw image data are assumed to be preprocessed according to the principles ofphotometric stereo. The two types of mea sured data were combined in accordance with the general concepts discussed in Part I of the paper. A computational example using synthetic data is presented and discussed.
Sensor Models and Multisensor Integration
Authors: Durrant-Whyte Hugh F.
Published: March 2007

We maintain that the key to intelligent fusion of disparate sensory information is to provide an effective model of sensor capabilities. A sensor model is an abstraction of the actual sensing process. It describes the information a sensor is able to provide, how this information is limited by the environ ment, how it can be enhanced by information obtained from other sensors, and how it may be improved by active use of the physical sensing device. The importance of having a model of sensor performance is that capabilities can be esti mated a priori and, thus, sensor strategies developed in line with information requirements.

We describe a technique for modeling sensors and the information they provide. This model treats each sensor as an individual decision maker, acting as a member of a team with common goals. Each sensor is considered as a source of uncertain geometric information, able to communicate to, and coordinate its activities with, other members of the sens ing team. We treat three components of this sensor model: the observation model, which describes a sensor's measure ment characteristics; the dependency model, which describes a sensor's dependence on information from other sources; and the state model, which describes how a sensor's observa tions are affected by its location and internal state. We show how this mechanism can be used to manipulate, communi cate, and integrate uncertain sensor observations. We show that these sensor models can deal effectively with cooperative, competitive, and complementary interactions between differ ent disparate information sources.
Singularities in Motion and Displacement Functions of Constrained Mechanical Systems
Authors: Litvin F.L. , Tan J.
Published: March 2007

A general approach for the determination of singularities in motion and displacement functions of manipulators and linkages is proposed. Singularities in motion of a manipula tor occur at positions where the parameters in motions of the end-effector become dependent, or when the end-effector is at rest and some manipulator links become movable. Singular ities in motion of a linkage occur at positions where an over- constrained group of links becomes mobile while the driving link is held at rest. Both cases of singularities are determined with the condition that the rank r of the system matrix of six linear equations is less than 6. The system of linear equa tions relates the velocities in motion in joints with the veloci ties of the linkage driving link (manipulator end-effector). In the proposed approach, the elements of the system matrix can be derived directly by using the matrix representation of coordinate transformation. The requirement r < 6 provides an equation (the singularity equation) that relates some parameters of motion. The structure of the singularity equa tion determines the structure of the to-be-derived displace ment equations. The derivation of displacement equations is based on (i) modeling of the manipulator or linkage by open subchains, and (ii) determination of invariants for the sub chains. The number of configurations that can be formed by linkage links is proposed to relate to the number of multiple singularity positions. A method for determination of multiple singularity positions is proposed. The proposed approach is illustrated with examples of manipulators and linkages.
Dynamics and Stability in Coordination of Multiple Robotic Mechanisms
Authors: Nakamura Yoshihiko , Nagai Kiyoshi , Yoshikawa Tsuneo
Published: March 2007

This paper discusses the dynamical coordination of multiple robot manipulators or a multifingered robot hand. The coor dination problem is divided into two phases: determining the resultant force by multiple robotic mechanisms; determining the internal force between mechanisms. The resultant force is used for maintaining dynamic equilibrium and for generat ing the restoring force. A dynamic coordinative control scheme which guarantees the object stability is proposed, associated with the determination of the resultant forces. The internal force is used to satisfy the static frictional constraints and is related to contact stability. The minimizing internal force is defined as the internal force which yields the minimal norm force satisfying static frictional constraints and the minimizing internal force is solved by applying a nonlinear programming method. The concept of the minimizing inter nal force is fundamental and important because it can theo retically answer whether the object can be grasped and ma nipulated with the given finger placement. Contact stability means the ability for the end-effector to maintain contact with an object without slipping when the object is subjected to disturbing external forces. A method of evaluating contact stability is developed. The minimal norm force satisfying the specified degree of contact stability can be obtained by using an algorithm similar to that for the minimizing internal force. Numerical examples of computing the minimizing in ternal forces are given.
Simulated Off-Line Programming of Welding Robots
Authors: Buchal R.O. , Cherchas D.B. , Sassani F. , Duncan J.P.
Published: March 2007

The objectives of the work described in this paper are to develop and evaluate a method for calculation of interference between objects in a robot welding workstation, to develop a robot trajectory planning technique recognizing interference, inverse kinematics constraints, and welding parameter re quirements, and to demonstrate the trajectory planning tech nique using advanced computer graphics. Workstation mod eling and relevant kinematic relationships are discussed. A method of interference calculation is developed which allows rapid calculation of interference between convex polyhedra using a steepest descent graph search. If desired, exact sepa rating distances and directions can be found. A simple mod ule for automatic selection of welding parameters is de scribed. Interference-free trajectories that do not violate kinematics constraints are found by searching among possi ble inverse kinematic solutions for the desired welding torch trajectory. The above methods have been combined and implemented using interactive graphics in a prototype soft ware package called A UTO WELD.
Geometrical Modeling from Multiple Stereo Views
Authors: Pollard S.B. , Pridmore T.P. , Porrill J. , Mayhew J.E.W. , Frisby J.P.
Published: March 2007

The components of the Sheffield Artificial Intelligence Vision Research Unit (AIVRU) three-dimensional (3D) vision sys tem, which currently supports model-based object recognition and location, are described. Its potential for robotics applica tions is demonstrated by its guidance of a Universal Machine Intelligence robot arm in a pick-and-place task. The system comprises (1) the recovery of a sparse depth map using edge- based, passive stereo triangulation; (2) the grouping, descrip tion, and segmentation of edge segments to recover a 3D representation of the scene geometry in terms of straight lines and circular arcs; (3) the statistical combination of 3D de scriptions for object model creation from multiple stereo views and the propagation of constraints for within-view re finement ; and (4) the matching of 3D wireframe object models to 3D scene descriptions in order to recover an initial estimate of their position and orientation.
Grasping and Coordinated Manipulation by a Multifingered Robot Hand
Authors: Zexiang Li  , Hsu Ping , Sastry Shankar
Published: March 2007

A new avenue of progress in the area of robotics is the use of multifingered robot hands for fine motion manipulation. This paper treats two fundamental problems in the study of multi fingered robot hands: grasp planning and the determination of coordinated control laws with point contact models. First, we develop the dual notions of grasp stability and grasp manipulability and propose a procedure for task modeling. Using the task model, we define the structured grasp quality measures, and using these measures we then devise a grasp planning algorithm. Second, based on the assumption of point contact models, we develop a computed torque-like con trol algorithm for the coordinated manipulation of a multi fingered robot hand. This control algorithm, which takes into account both the dynamics of the object and the dynamics of the hand, will realize simultaneously both the position trajec tory of the object and any desired value of internal grasp force. Moreover, the formulation of the control scheme can be easily extended to allow rolling and sliding motion of the fingers with respect to the object.
Compensation of Industrial Manipulator Dynamics
Authors: Leahy M.B. , Saridis G.N.
Published: March 2007

Experimental evaluations have demonstrated the effect of dynamic compensation on the trajectory tracking accuracy of industrial manipulators. High gear ratios reduce the compu tational complexity of the system dynamics but do not elimi nate the requirement for accurate modeling. For the PUMA-560 case study, the motor dynamics were experimen tally determined and combined with link dynamics to accu rately model the complete system. The impact from compen sating for specific manipulator dynamics by feedforward and computed-torque controllers was then experimentally deter mined. Feedforward dynamic compensation reduced the peak trajectory tracking errors of an independent joint Pro portional Derivative controller by a factor of three. The com bination of high sample rates and feedforward dynamic compensation produced a control algorithm with excellent peak and final error.
Forward Calibration of Closed-Loop Jointed Manipulators
Authors: Everett Louis J.
Published: March 2007

A method for performing forward kinematic calibration of manipulators with one or more closed-loop actuated joints is presented. The technique is an extension of algorithms de signed for open-loop jointed manipulators and is equivalent to minimizing a constrained objective function. The con straints arise from the closed-loop mechanisms in the manip ulator. The objective function is taken as the integral of end effector position and orientation error and is optimized using the method of Lagrange multipliers.
Robot Path Planning with Obstacles, Actuator, Gripper, and Payload Constraints
Authors: Shiller Zvi , Dubowsky Steven
Published: March 2007

A method is presented to obtain the time-optimal motions for robotic manipulators. It considers the full nonlinear dy namics of the manipulator, its actuator saturation limits, and gripper and payload constraints. It also accounts for both the presence of obstacles in the work space and restrictions on the motion of the manipulator's joints. The method is com putationally practical and has been implemented for the optimal trajectory planning of general six degree-of-freedom manipulators. Examples are presented that demonstrate the substantial improvement in manipulator performance that can be achieved using this method.
The Singular Value Decomposition: Computation and Applications to Robotics
Authors: Maciejewski Anthony A. , Klein Charles A.
Published: March 2007

The singular value decomposition has been extensively used for the analysis of the kinematic and dynamic characteristics of robotic manipulators. Due to a reputation for being nu merically expensive to compute, however, it has not been used for real-time applications. This work illustrates a for mulation for the singular value decomposition that takes advantage of the nature of robotics matrix calculations to ob tain a computationally feasible algorithm. Several applica tions, including the control of redundant manipulators and the optimization of dexterity, are discussed. A detailed illus tration of the use of the singular value decomposition to deal with the general problem of singularities is also presented.
The Singularities of Redundant Robot Arms
Authors: Shamir T.
Published: March 2007

A robot arm is redundant if it has extra degrees offreedom. In such cases the kinematic function is a mapping from a higher-dimensional joint space to a lower-dimensional work space. The manipulator may have singular configurations, which are singularities of the kinematic function. At or near the singularities, the robot may be difficult to control. The redundancy may help to avoid some singularities, but other singularities may be unavoidable. To help in the robot design and in order to devise a controlling strategy that would avoid singularities, it is important to know analytically which singularities are avoidable. This paper gives some tools for classifying singularities. The singularities of 3-joint manipu lators operating in 2-dimensional work spaces are classified, and an analysis is performed for case studies, with various manipulator designs.
Stability and Robustness Analysis of a Class of Adaptive Controllers for Robotic Manipulators
Authors: Sadegh Nader , Horowitz Roberto
Published: March 2007

The stability and robustness properties of the adaptive control scheme proposed by Sadegh and Horowitz (1987) are stud ied. The properties include the global exponential stability and Lp input/output stability of the nonadaptive (i.e., fixed- parameter) control system and the global asymptotic stability of the adaptive control scheme. Sufficient conditions for the convergence of the estimated parameters to their true values are also given. A computationally efficient adaptation scheme that is a modified version of the original scheme is proposed. The modified scheme utilizes the desired trajectory outputs, which can be calculated a priori, instead of the actual joint outputs in the parameter adaptation algorithm and the non linearity compensation controller. Sufficient conditions for guaranteeing all the stability properties of the original scheme in the modified scheme are also explicitly derived. A com puter simulation study of the performance of both schemes in the presence of noise disturbances is conducted.
A Dataflow Multiprocessor System for Robot Arm Control
Authors: Geffin Steve , Furht Borko
Published: March 2007

With the development of robot control theory, there has been an increased demand for more efficient robot control schemes. The real-time computation of applied torques in nonlinear and strongly coupled multi-link systems is compli cated and time consuming. This paper proposes a dataflow multiprocessor system for robot arm control. The proposed architecture computes the applied torques of a multi-link system using the Newton-Euler state space formulation. Sim ulation studies have verified the effectiveness of the proposed architecture by producing execution times that are fast enough for real-time control application. The architecture that explores the maximum parallelism would consist of 1834 processing elements; however, a reasonable engineering solution consists of 42 processing elements. If this dataflow architecture with reduced number of processing elements is implemented using currently available fast-processing ele ments (40 ns multipliers and adders), it calculates the torque for a six-link robotic system in 1.02 ms. The system is simu lated using Transputers and the language Occam.
Minimum-Speed Motions
Authors: Aronov Boris , Fortune Steven , Wilfong Gordon
Published: March 2007

We consider the problem of determining how fast an object must be capable of moving for it to be able to reach a given position at a given time while avoiding moving obstacles. The problem is to plan velocity profile along a given path so that collisions with moving obstacles crossing the path are avoided and the maximum velocity along the path is mini mized. Suppose the time-varying environment is fully speci fied, both in space and in time, by n linear constraints. An algorithm is presented that, given a full description of the environment and the initial configuration of the system (that is, initial position and starting time of the object), answers in O(log n) time queries of the form : "What is the lowest speed limit that the object can obey while still being able to reach the query configuration from the initial configuration without colliding with the obstacles?" The algorithm can also be used to compute a motion from the initial configuration to the query configuration that obeys the speed limit in O (n ) time. The algorithm requires O (n log n) preprocessing time and O (n) space.