bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Influence Diagrams to Structure Medical Decisions
Authors: Nease Robert F. , Owens Douglas K.
Published: March 2007

Influence diagrams are compact representations of decision problems that are mathematically equivalent to decision trees. The authors present five important principles for structuring a decision as an influence diagram: 1) start at the value node and work back to the decision nodes; 2) draw the arcs in the direction that makes the probabilities easiest to assess; 3) use informational arcs to specify which events will have been observed at the time each decision is made; 4) ensure that missing arcs reflect intentional assertions about conditional independence and the timing of observations; and 5) ensure that there are no cycles in the influence diagram. They then build an influence diagram for the problem of staging non-small-cell lung cancer as an illustration. Influence diagrams offer several strengths for structuring medical decisions. They represent graphically and compactly the probabilistic relationships between parameters in the model. Influence diagrams also allow the model to be structured in a fashion that eases the necessary probability assessments, regardless of whether the assessments are based on available evidence or on expert judgment. Influence diagrams provide an important complement to decision trees, especially for representing probabilistic relationships among variables in a decision model. Key words : decision analysis; influence diagrams; decision tree; decision techniques; cost-effectiveness analysis. (Med Decis Making 1997;17:263-275)
Making Treatment Decisions with HIV Infection:
Authors: Rosenfeld Barry D. , White Mary , Passik Steven D.
Published: March 2007

The importance of understanding patient preferences in making treatment decisions is widely recognized. This pilot study utilized a forced-choice paired-comparison method in which 28 ambulatory HIV-infected patients were given a computer-generated presentation of all possible pairs of eight different treatment options for their disease (FDAapproved medications, experimental and alternative treatments, no medication). Preferences were analyzed using binary multidimensional scaling analyses to determine the utility of paired-comparison models for the study of treatment-decision making and to identify factors influencing patient decision making. Results indicated that a three-dimensional model provided the best fit for the data. One dimension correlated with medications that raise CD4+ lymphocyte counts (r = 0.92, p < 0.001) and a second dimension correlated with frequency of dosing (r = 0.97, p < 0.0001). Patients' internal consistency of decision making was inversely correlated with severity of AIDS dementia symptoms as measured by performance on a neuropsychological test battery (r = -0.55, p < 0.0025). This finding indicates that AIDS dementia may significantly hinder patients' ability to use a rational (internally consistent) decision-making strategy in making treatment choices. Results also suggested that AIDS patients base treatment decisions primarily on the likelihood of raising CD4+ cell counts and restrictiveness of dosing regimens, but are not influenced by FDA approval status, volume of empirical support for the medications, or even possible harmful side effects. The implications of these findings for the treatment of patients with AIDS are discussed. Key words: treatment decisions; patient preferences; HIV infection; AIDS; informed consent. (Med Decis Making 1997;17:307-314)
Exorcising Protocol-induced Spirits:
Authors: Rittenhouse Brian E.
Published: March 2007

Economic evaluation frequently depends on estimates from clinical trials of both effectiveness of treatment and resource utilization accompanying it. Protocol-driven events in the trial among other influences often imply that both estimates will be inaccurate. This paper indicates how one may supplement a trial with additional data to connect the artificial trial to the real world of clinical practice. It also shows that data required for this model may be estimated from other sources (via Bayesian modeling) if they are not directly available. The required data include (for example) the proportion of patients with disease who would have presented with clinical signs if they had not been part of a trial that allowed early detection and treatment based on subclinical testing mandated by trial protocol. Those presenting with clinical signs would use additional resources for treatment and/or confirmatory diagnostics. Those with subclinical disease either 1) would never use resources in the case where they never developed clinical manifestations or 2) would use resources of a different type or intensity and perhaps have different outcomes by virtue of their disease's being discovered at a later point in time. Basing resource use and ultimate effectiveness on this revised measure of outcome rather than the one in the trial should lead to more accurate predictions for economic purposes. Key words: economic evaluation; external validity; effectiveness ; bias; modeling. (Med Decis Making 1997;17:331-339)
Hepatitis B Immunization in a Low-incidence Province of Canada
Authors: Wiebe Tim , Fergusson Patricia , Horne Digby , Shanahan Marian , Macdonald Anna , Heise Lynn , Roos Leslie L.
Published: March 2007

This study provides a comparative cost-effectiveness analysis of three universal im munization programs for hepatitis B virus (HBV). Using three theoretical cohorts of infants, 10-year-olds, and 12-year-olds, a universal immunization program was com pared with a prenatal screening/newborn immunization program involving testing of prepartum women and immunization of newborns of HBsAg-positive mothers. A Mar kov long-term outcome model used Manitoba data to estimate costs and health out comes across the lifespan. The model was based on an HBV incidence rate of 19/ 100,000 and a discount rate of 5% and incorporated the most recent treatment ad vances (interferon therapy). Cost-effectiveness was calculated as the ratio of dollars spent per year of life saved, with costs determined from the perspective of a third- party payer. The universal infant-immunization program, although not cost-saving, was associated with a low, economically attractive cost-effectiveness ratio of $15,900 (Ca nadian) per year of life saved, a figure substantially lower than the ratios of $97,600 and $184,800 (Canadian) associated with the universal programs for 10- and 12-year- olds, respectively. Cost-effectiveness ratios were found to be sensitive to changes in immunization costs, HBV incidence rates, and the rate at which protective antibody levels are lost over time: If these variables move in the directions suggested by current trends, the authors anticipate an increasing economic appeal of universal programs well into the future. A universal program of HBV immunization for infants appears to be economically practical in regions where HBV infection rates are low and stable. Key words: hepatitis B; cost-effectiveness; immunization. (Med Decis Making 1997; 17:472-482)
Estimating CE Ratios under Second-order Uncertainty
Authors: Stinnett Aaron A. , Paltiel A. David
Published: March 2007

Two methods have been presented for estimating cost-effectiveness ratios under con ditions of second-order (model) uncertainty: one method estimates a mean ratio of cost to effect (the "mean ratio" approach), and the other estimates a ratio of mean cost to mean effect (the "ratio of means" approach). However, the question of which estimate is theoretically correct has not been formally addressed. The authors show that the "ratio of means" approach follows directly from the theoretical foundations of cost-effectiveness analysis, has attractive internal consistency properties, and is con sistent with a simple vector algebra approach to the problem. In contrast, the "mean ratio" approach has not been shown to follow from first principles, is internally incon sistent, and can prescribe economically inefficient choices. It is concluded that the "ratio of means" procedure should be preferred unless persuasive arguments are pre sented to the contrary. Key words: cost-effectiveness analysis; mean ratio; ratio of means; second-order uncertainty. (Med Decis Making 1997;17:483-489)
The Ontario Health Care Evaluation Network and the Critical Care Research Network as Vehicles for Research Transfer
Authors: Sibbald William J. , Kossuth Jennifer D.
Published: March 2007

Facilitating the successful and consistent use of research results to support health care decisions is a formidable task. Barriers to effectively transferring the results of research into the decision-making process have been created between practitioners and researchers, who traditionally have worked in isolation from each other. The need for them to work cooperatively to break down these barriers is paramount as changes within the health care environment increase. The Ontario Health Care Evaluation Net work (OHCEN) and the Critical Care Research Network (CCR-Net) have attempted to address these concerns by bringing together teams of researchers, practitioners, and administrative personnel with the purpose of equipping them with tools to meet on coming health care challenges. Key words: research transfer; decision making; evi dence-based medicine; systematic reviews; meta-analysis; education; informatics; In ternet; communications. (Med Decis Making 1998;18:9-16)
Uncertainty in Decision Models Analyzing Cost-Effectiveness
Authors: Hunink Maria G.M. , Bult Jan Roelf , De Vries Jelle , Weinstein Milton C.
Published: March 2007

Purpose. To illustrate the use of a nonparametric bootstrap method in the evaluation of uncertainty in decision models analyzing cost-effectiveness. Methods. The authors reevaluated a previously published cost-effectiveness analysis that used a Markov model comparing initial percutaneous transluminal angioplasty with bypass surgery for femoropopliteal lesions. Each probability in the model was simulated with a first-order Monte Carlo simulation to represent sampling uncertainty. Superimposed on this, a second-order Monte Carlo simulation was performed to represent parameter uncer tainty, drawing the probability values from nonparametric distributions based on published data or from primary collected data as available. After simulation of a mixed (i.e., non-idenfical) cohort of 30,000 patients, 3,000 bootstrap samples of 1,000 pa tients each were drawn and the joint distribution of mean incremental costs and mean effectiveness gained was evaluated. Results. Using a bootstrap sample size of 1,000 patients, 92.7% of the joint distribution of mean incremental costs and mean effective ness gained fell in the quadrant where angioplasty dominated bypass surgery. Another 6.9% of samples demonstrated either greater effectiveness with an incremental cost- effectiveness ratio of at most $20,000/QALY gained, or cost savings with a ratio of at least $20,000 saved/QALY lost. Conclusion. A nonparametric bootstrap method can be used to estimate the joint distribution of mean incremental costs and mean effec tiveness gained, and the results can provide an understanding of the uncertainty in a cost-effectiveness analysis based on a decision model. Key words: cost-effective ness analysis; sensitivity analysis; Monte Carlo simulation; Markov models; bootstrap ping. (Med Decis Making 1998;18:337-346)
Management of Unruptured Intracranial Aneurysm in Japan
Authors: Aoki Noriaki , Kitahara Takao , Fukui Tsuguya , Beck J. Robert , Soma Kazui , Yamamoto Wari , Kamae Isao , Ohwada Takashi
Published: March 2007

The purpose of this study was to analyze the management of individual patients with unruptured intracranial aneurysms (UN-ANs) using a decision-analytic approach. Tran sition probabilities among Glasgow Outcome Scale (GOS) categories were estimated from the published literature and data from patients who had been treated at Kitasato University Hospital. Utilities were obtained from 140 health providers based principally on the GOS. Baseline analysis for a healthy 40-year-old man with an anterior UN-AN less than 10 mm in diameter showed that the quality-adjusted life expectancies for preventive operation and follow-up were 15.34 and 14.66 years, respectively. For a follow-up strategy to be preferred, the annual rupture rate had to be as low as 0.9%. These results were sustained through extensive sensitivity analysis. The results sup port preventive operation for UN-ANs, and identify problems that can be clarified with a well-designed stratified clinical trial. Key words: decision analysis; Markov model; unruptured intracranial aneurysms; Glasgow Outcome Scale; utility; preventive oper ations. (Med Decis Making 1998;18:357-364)
Estimating General-population Utilities Using One Binary-gamble Question per Respondent
Authors: Bosch Johanna L. , Hammitt James K. , Weinstein Milton C. , Hunink Maria G.M.
Published: March 2007

This study used a single binary-gamble question per health state per respondent to obtain societal preferences for the health states intermittent claudication and major amputation and compare those with Health Utilities Indices obtained from patients, to test the feasibility of this method, and to investigate whether the utility depends on the presentation of a vignette as generic vs disease-specific. A random sample of the general U.S. population (n = 1,003) was randomly divided into ten subgroups. In tel ephone interviews, subjects answered one binary-gamble question in a standard-gam ble format for each of two health states. The risks of death varied across subgroups but not between health states. Mean utility was estimated by the area above the pro portional distribution of responses indicating acceptance of the gamble. The method is based on the binary-choice method used in contingent-valuation studies of willing ness to pay. The health states were alternatively described by generic and disease- specific vignettes in two subsamples. The results suggest that the binary-gamble ques tion can be used to obtain societal preferences for health states, and that disease-specific descriptions yield lower utilities compared with generic descriptions of health states. Key words: peripheral arterial occlusive disease, intermittent claudica tion ; quality of life; standard gamble; utility assessment. (Med Decis Making 1998;18: 381-390)
A Method for Evaluating Health Care Providers' Decision Making
Authors: Dolan James G.
Published: March 2007

Valid and reliable assessment of the clinical decision-making process is essential for the evaluation of decision aiding methods and effective quality assurance programs. The Provider Decision Process Assessment Instrument is a 12-item questionnaire that measures a health care provider's degree of comfort with a medical decision. Its mea surement properties were studied in two general internal medicine practices. Reliability, measured using Cronbach's alpha, was 0.90 (95% CI = 0.87 to 0.92). Construct validity was also high, with expected negative correlations ranging from -0.53 to -0.67. The instrument also satisfied standard criteria for item homogeneity and was readily com pleted by clinicians. These results suggest that the Provider Decision Process As sessment Instrument will prove to be a valuable tool for assessing medical decision making in busy clinical settings. Key words: decision making; decision support sys tems ; quality assessment. (Med Decis Making 1999;19:38-41)
Analysis of Three Decision-making Methods
Authors: Carter Kimbroe J. , Ritchey Nathan P. , Castro Frank , Caccamo Leonard P. , Kessler Edward , Erickson Barbara A.
Published: March 2007

Purpose: To compare three decision making techniques using a common clinical prob lem. Methods: Two recently developed methods, the analytic hierarchy process (AHP) and the analytic network process (ANP), were compared with a Markov process in the evaluation of the optimal post-lumpectomy treatment strategy for an elderly woman with a mammographically detected, nonpalpable early-stage breast cancer. The follow ing treatment alternatives were considered: observation, radiation, tamoxifen, combi nation radiation and tamoxifen, and simple mastectomy. All three decision methods incorporated patient preferences. Results: The models agreed on the ranking of the preferred treatment, radiation and tamoxifen, but there were variations in the rankings of the other treatment choices. Individual differences between the three models were uncovered. The Markov process provided estimates of quality-adjusted life expectancy and distribution of health events. Both AHP and ANP required less development time than the Markov process. Conclusion: All three methods may be useful tools to the clinician in analyzing complex medical problems. The Markov is the most labor-inten sive method but provides detailed results, whereas the AHP and the ANP give only rank orders of the alternatives. The most important considerations in choosing between these methods are time to project completion and the detail of information sought. Key words: breast cancer; Markov process; analytic hierarchy process; analytic network process. (Med Decis Making 1999;19:49-57)
The Relationship between Health-state Utilities and the SF-12 in a General Population
Authors: Lundberg Lena , Johannesson Magnus , Isacson Dag G.L. , Borgquist Lars
Published: March 2007

It would be a major advance if quality-of-life instruments could be translated into health- state utilities. The aim with this study was to investigate the relationship between the SF-12 and health-state utilities, based on responses to a postal questionnaire sent to a random sample of 8,000 inhabitants, aged 20-84 years, in the general population. The questionnaire included the SF-12, a rating-scale (RS) question, and a time-tradeoff (TTO) question; the response rate was 68%. Age, gender, and the 12 items of the SF- 12 were used as explanatory variables in a linear regression analysis of the health- state utilities. The regression models explained about 50% of the variance in the RS answers and about 25% of the variance in the TTO answers. Most of the SF-12 items were related to the health-state utilities in the expected ways, with especially strong results for the RS method. The results suggest that the SF-12 can be converted to health-state utilities, but that further work is needed to reliably estimate the conversion function. Key words: health status; SF-12; rating scale; time-tradeoff; health-related quality of life; health-state utilities; population study. (Med Decis Making 1999;19:128- 140)
Time Preferences and Preventive Health Behavior
Authors: Chapman Gretchen B. , Coups Elliot J.
Published: March 2007

Background. Many preventive health behaviors involve immediate costs and delayed benefits. Time preference is the extent to which decision makers value future outcomes relative to immediate ones. Consequently, people with future-oriented time preferences should be more likely to adopt preventive measures. The relationship between time preferences and acceptance of a free influenza vaccination was examined. Sample. The participants were 412 corporate employees who were offered free influenza vac cinations at their workplace. Measures. Participants' time preferences were measured in each of two domains: money and health. They also reported on whether they had accepted the influenza vaccination and their beliefs and attitudes about the vaccine. Results. There was a small (OR = 2.38) relationship of vaccination acceptance to monetary time preferences but not to the health time-preference measures. Other var iables, such as perceived effectiveness of the vaccine, were more predictive. Conclu sion. This study provides some evidence of a small relationship between time prefer ences and preventive health behavior. Key words: time preference; decision making; preventive health behavior; influenza vaccine. (Med Decis Making 1999; 19:307-314)
Inconsistencies in the "Societal Perspective" on Costs of the Panel on Cost-Effectiveness in Health and Medicine
Authors: Meltzer David , Johannesson Magnus
Published: March 2007

A key recommendation of the recent Panel on Cost-Effectiveness in Health and Med icine was that cost-effectiveness analyses be carried out from a societal perspective. The authors show that two of the Panel's recommendations concerning costs are not consistent with a societal perspective, and how to correct those inconsistencies. In its recommendations concerning costs resulting from morbidity, the Panel advises ex cluding lost income from costs in the belief that individuals take income changes into account when they respond to the quality-of-life questions that are used to calculate quality-adjusted life years (QALYs). It is shown that even if individuals do consider income changes in responding to these quality-of-life questions, this recommendation would seriously underestimate production losses due to morbidity, since individuals do not bear a major part of lost production. In its recommendations concerning costs resulting from mortality, the Panel does not require that health care costs for "unre lated" illness and non-health care consumption and production during added life years be included in the Reference Case. It is shown that omitting these costs will seriously distort comparisons of programs at different ages and favor programs that extend life over those that improve quality of life. This can be corrected by including total con sumption minus production in added life-years among costs. Key words: cost-effec tiveness analysis; societal perspective; public policy; resource allocation; Panel on Cost-Effectiveness in Health and Medicine. (Med Decis Making 1999; 19:371-377)
How Should Effectiveness of Risk Communication to Aid Patients' Decisions Be Judged?
Authors: Edwards Adrian , Elwyn Glyn
Published: March 2007

Risk-communication interventions are associated with benefits at both the individual and the public health level. However, the types of outcomes used to assess the effec tiveness of risk-communication interventions vary greatly. This makes synthesis of the research in systematic review difficult, and limits both the implementation of advances in clinical practice and further research. This article reviews the outcomes used in risk- communication publications, particularly those addressing individual decisions about treatment. From the traditional cognitive and behavioral research outcomes of patient knowledge, risk perception, and compliance, the emphasis has shifted towards more affective outcomes, including satisfaction, assessment of the information provided and the decision-making process, and certainty about whether the best option has been chosen. These affective outcomes may be more specific and sensitive measures for risk-communication research. Further development and validation of measurement scales to address these issues is needed. Key words: risk communication; physician- patient communication; outcome assessment; affective outcomes. (Med Decis Making 1999;19:428-434)
Do People Value Their Own Future Health Differently from Others' Future Health?
Authors: Cairns John , Van Der Pol Marjon
Published: March 2007

The purpose of this study was to investigate whether time preferences for own health are the same as time preferences for others' health. A random sample of the general public was sent a postal questionnaire containing six choices between ill health in the near future and ill health in the further future. They were asked to indicate the maximum duration of more distant ill health they would be willing to accept in return for a specified delay in the onset of the period of ill health. For half of the sample the questions were set in the context of their own health and for the other half in terms of others' health. The median implied discount rates were not statistically different, 0.061 for own health and 0.062 for others' health. A multilevel analysis of the determinants of these implied discount rates provided additional evidence of the similarity of time preferences for own health and others' health. Key words: intertemporal preferences; own versus other's health. (Med Decis Making 1999; 19:466-472)
Whose Preferences Count?
Authors: Dolan Paul
Published: March 2007

An important consideration when choosing how to allocate health care resources is the improvements in patients' health-related quality of life (HRQoL) that alternative allocations generate. There is considerable debate about whose preferences should be used when measuring and valuing HRQoL. This debate has usually been in terms of whether the values of patients or the general public are the most appropriate. It is argued in this paper that this is a false dichotomy that does not facilitate understanding of empirical evidence. Nor, more importantly, does it address one of the most important issues in the debate about whose preferences count, that is, whether the fact that many people adapt to poor health states should be taken into account when ascribing values to those states. A conceptual framework is developed to facilitate a more fruitful discussion of the issues relating to the question of whose preferences should count. Key words: health-related quality of life; patients' preferences; resource allocation; elicitation methods. (Med Decis Making 1999; 19:482-486)
Articulated Hands
Authors: Salisbury J. Kenneth , Craig John J.
Published: March 2007

Kinematic and control issues are discussed in the context of an articulated, multifinger mechanical hand. Hand designs with particular mobility properties are illustrated, and a definition of accuracy points within manipulator workspace is given. Optimization of tlte physical dimensions of the Stanford-JPL hand is described. Several architectures for position and force control of this multiloop mechanism are described, including a way of dealing with the internal forces inherent in such systems. Preliminary results are shown for the joint torque subsystem used in the hand controller.
Survey of Model-Based Image Analysis Systems
Authors: Binford Thomas O.
Published: March 2007

A survey and critique of the state of the art in model-based image analysis systems is presented. The paper includes summaries of a selection of systems and evaluates them from the viewpoint of progress toward general vision systems. The paper also describes principles of design of general vision systems.
Supervisory Control of a Multilegged Robot
Authors: Orin David E.
Published: March 2007

Motion-planning algorithms to provide for 3-axis joystick control of a multilegged robot over planar terrain are presented. Three different modes of operation are developed: cruise (for motion along the circular arc whose radius varies with joystick position), side-stepping, and turn-in-place. In each of these modes, the trajectories of the body and the feet are generated. The overall cycling of the legs defines a "wave" gait pattern. The algorithms have been implemented on a PDP-11/45 minicomputer, and results for the control of the OSU Hexapod are given.
Is Dynamic Control Needed in Robotic Systems, and, if So, to What Extent?
Authors: Vukobratović M. , Stokić D.
Published: March 2007

The problem of dynamic control in robotic systems is considered in this paper. Robotic systems are essentially dynamic systems. The problem is whether is it necessary to take dynamics into account in controlling them, and, if so, to what extent. In cases of slow motion and mechanical configuration with weakly coupled subsystems ( mechanical degrees of freedom ) it is not necessary to solve the control task dynamically. In cases of faster motion and mechanical configuration with strongly coupled subsystems, however, the control task is essentially dynamic and we suggest some control strategies which include complete dynamics of the robot. Several examples of locomotion and manipulation robots' control synthesis are presented. We present postural stabilization of biped robot, as a representative of dynami cally unstable locomotion robots. The control synthesis for three types of manipulation robots is described in order to show how the extent of inclusion of dynamics in the control depends on the mechanical configuration of a robot.
A Torque-Sensitive Tactile Array for Robotics
Authors: Hackwood S. , Beni G. , Hornak L.A. , Wolfe R. , Nelson T.J.
Published: March 2007

We introduce a new tactile sensor and show its advantages for robotic applications. The tactile array elements are composed of magnetic dipoles (in an elastic medium) whose position and orientation are detected by magnetoresistive sensors. We show that, unlike the existing tactile sensor designs, this device is sensitive to torque as well as to normal and tangential forces. We demonstrate experimentally the fabrication, sensitivity, and repeatability of the tactile elements.
Recursive Lagrangian Dynamics of Flexible Manipulator Arms
Authors: Book Wayne J.
Published: March 2007

Nonlinear equations of motion are developed for flexible manipulator arms consisting of rotary joints that connect pairs of flexible links. Kinematics of both the rotary-joint mo tion and the link deformation are described by 4 X 4 trans formation matrices. The link deflection is assumed small so that the link transformation can be composed of summations of assumed link shapes. The resulting equations are pre sented as scalar and 4 X 4 matrix operations ready for pro gramming. The efficiency of this formulation is compared to rigid-link cases reported in the literature.
Efficient Computation of the Jacobian for Robot Manipulators
Authors: Orin David E. , Schrader William W.
Published: March 2007

This paper discucsses and compares six different methods for calculating the Jacobian for a general N-degree-of freedom manipulator. We enumerate the computational efficiency of each in terms of the total number of multiplications, addi tions/subtractions, and trigonometric functions required as well as in terms of the number of matrix-vector operations needed. We also give the execution times on a PDP-11/70 minicomputer for determining the Jacobian for an example seven-degree-of-freedom manipulator. This paper formulates one of the best new methods for determining the Jacobian.
Manipulability of Robotic Mechanisms
Authors: Yoshikawa Tsuneo
Published: March 2007

This paper discusses the manipulating ability of robotic mechanisms in positioning and orienting end-effectors and proposes a measure of manipulability. Some properties of this measure are obtained, the best postures of various types of manipulators are given, and a four-degree-of-freedom finger is considered from the viewpoint of the measure. The pos tures somewhat resemble those of human arms and fingers.
Analysis of Multifingered Hands
Authors: Kerr Jeffrey , Roth Bernard
Published: March 2007

This paper discusses three fundamental problems relating to grasping and manipulating objects within an articulated, multifingered hand: determining how hard to squeeze an ob ject in order to ensure a secure grasp, determining the finger- joint motions required to produce a desired motion of the object, and determining the workspace of the hand.

Squeezing the object, or the application of internal grasp forces, is reduced to a linear programming problem which considers friction and joint torque limit constraints. The relationship between the finger-joint motions and the motion of the object, for the case of pure rolling between the finger tips and the object, is formulated as a set of differential equa tions. The total workspace for a hand is determinedfor spe cial cases of planar and spatial hands.
Synthesis of 7-R Spatial Motion Generators with Prescribed Crank Rotations and Elimination of Branching
Authors: Sandor George N. , Yongxian Xu  , Weng Tzu-Chen
Published: March 2007

The paper presents conditions for avoidance of branching in the synthesis of 7-R spatial mechanisms. These conditions are based on the theory of linearly dependent screws by Hunt (1978) and on the theory about the existence of tangent loci in the so-called stationary configuration of the mechanisms (Sandor and Zhuang 1984a and b). First, the conditions for stationary configuration are obtained on the basis of the above-mentioned theories. Then, since the related branches are at both sides of the special canfiguration, corresponding conditions for avoidance of branching are obtained. Finally, we present a numerical example of the synthesis of a 7-R spatial motion generator with prescribed finitely separated positions, prescribed crank rotations, and with application of branching defect avoidance.
3DPO: A Three- Dimensional Part Orientation System
Authors: Bolles Robert C. , Horaud Patrice
Published: March 2007

In this paper, we present a system that recognizes objects in a jumble, verifies them, and then determines some essential configurational information, such as which ones are on top. The approach is to use three-dimensional models of the objects to find them in range data. The matching strategy starts with a distinctive edge feature, such as the edge at the end of a cylindrical part, and then "grows" a match by add ing compatible features one at a time. (The order of features to be considered is predetermined by an interactive, off-line, feature-selection process.) Once a sufficient number of com patible features has been detected to allow a hypothesis to be formed, the verification procedure evaluates it by comparing the measured range data with data predicted according to the hypothesis. When all the objects in the scene have been hy pothesized and verified in this manner, a configuration- understanding procedure determines which objects are on top of others by analyzing the patterns of range data predicted from all the hypotheses. We also present experimental results of the system's performance in recognizing and locating castings in a bin.
Two-Dimensional, Model-Based, Boundary Matching Using Footprints
Authors: Kalvin Alan , Schonberg Edith , Schwartz Jacob T. , Sharir Micha
Published: March 2007

In this paper, we describe a technique for geometrically hash ing two-dimensional model objects. Used in conjunction with other methods for recognizing partially obscured and over lapping objects, this technique enables us to recognize over lapping, two-dimensional objects selected from large data bases of model objects without significant performance degradation when the database is enlarged. This technique is based on use of a synthetic attribute of an object, which we will call its footprint. Experimental results from databases of up to 100 objects are presented.
A Comparative Study of Generalized Coordinates for Solving the Inverse- Kinematics Problem of a 6R Robot Manipulator
Authors: Low K.H. , Dubey R.N.
Published: March 2007

This paper studies two different approaches to the inverse- kinematics problem for a six-degree-of-freedom robot manip ulator having three revolute joint axes intersecting at the wrist. One method uses three rotational generalized coordi nates to describe the orientation of the body. The other method uses equivalent Euler parameters with one constraint equation. These two approaches have been incorporated into two different computer algorithms, and the results from each are compared on the basis of computational complexity, time simulation, singularity, etc. It was found that Euler parame ters were less efficient than three rotational angles for solving the inverse-kinematics problem of the robot considered, and that the physical singularities caused by the robot mecha nism could not be eliminated by using either of the two ap proaches.
Using Vision Data in an Object-Level Robot Language — RAPT
Authors: Yin B.
Published: March 2007

This paper describes the use of verification vision in an ob ject-level language for robot assembly (RAPT). In particular, a representation scheme for making full use of vision infor mation to update the robot system's knowledge about its environment is discussed. By using newly introduced vision commands, the user can specify vision verification tasks in order to determine the difference between the planned posi tions and the actual positions of objects in the robot's envi ronment. A symbolic reasoning system reasons about the spatial constraints at compile time and produces symbolic position expressions of the objects to be verified, which con tain variables to be instantiated by vision data at run time. A framework for handling vision data combines run time and compile time information in a general way so that all ramifi cations of the effect of the changed position determined by verification vision are taken into account. The new vision commands and the framework will be discussed in detail.
Feedback Control of a Flexible Manipulator with a Parallel Drive Mechanism
Authors: Matsuno Fumitoshi , Fukushima Shigenobu , Ohsawa Yoshiki , Kiyohara Makoto , Sakawa Yoshiyuki
Published: March 2007

A flexible manipulator having a parallel drive mechanism is treated. Only the forearm of the manipulator is assumed to be flexible, because it is slender and carries a heavy end-ef fector. The elastic vibration of the arm, which is due to its flexibility, and the position of the driving motors should be controlled simultaneously. On the basis of the mathematical model developed in our previous paper, we construct an optimal feedback control system by using the outputs of sev eral sensors. A set of experiments for the point-to-point position control was carried out with a microcomputer, which controls the whole servo system and plays the role of dynamic compensator. Several satisfactory experimental results are shown.
Compliant Robot Motion I. A Formalism for Specifying Compliant Motion Tasks
Authors: De Schutter J. , Van Brussel H.
Published: March 2007

A formalism is developed for specifying compliant motion tasks. It is based on the hybrid control functional specification method described by Mason. However, some new concepts are introduced: tracking directions, end-effector and task- frame motion constraints, feedforward velocity data, and task termination conditions. This formalism synthesizes all the information required in order to allow a completely auto matic execution of the task. As a result, it achieves strict separation between programming and control, which is of primary importance for the integration of compliant motion into a robot programming language. Several examples show that the formalism applies to a broad class of compliant motion tasks. The newly defined tracking directions contrib ute to the autonomy of the robot control system in case only partial geometric information about the environment is avail able.
Compliant Robot Motion II. A Control Approach Based on External Control Loops
Authors: De Schutter J. , Van Brussel H.
Published: March 2007

A control approach for the execution of robot tasks in contact with the environment is worked out. The input to the con troller consists of the task specification described in part I. The control approach is based on external force and tracking loops, which are closed around the robot positioning system. The position control loops tend to decouple and linearize the complex robot dynamics, and therefore they present to the external controllers a system which is easy to model and easy to control. Design and properties of external control loops are discussed in great detail. In particular, the role of a passive compliance with respect to task execution speed and distur bance rejection is analyzed both qualitatively and quantita tively. The resulting compliant motion controller has been tested experimentally, and proved to be very robust and to yield the theoretically expected performance.
A Robotic Perceptual System Utilizing Passive Vision and Active Touch
Authors: Stansfield S.A.
Published: March 2007

This paper presents a robotic perceptual system which utilizes passive vision and active touch. The task is one-fingered exploration of a single unmodeled object for apprehension— the determination of the features of the object and the rela tions among them. A two-stage exploration is utilized. Vision is first used in a feedforward manner to segment the object and to obtain its position. Touch is then used in a feedback mode to further explore the object. In designing this system, we have addressed several issues. The first concerns the way in which the robotic perceptual system should be structured. The model which we propose here is based upon theories of human perception. It consists of a highly modularized set of knowledge-based modules, each of which is domain specific and informationally encapsulated. Within the framework of this model, we have designed both vision and touch subsys tems. In each case, we have defined the primitives, features, and representations extracted and created by the system. The visual system is passive and relatively simple. The touch system is active and is an attempt to systematically structure a robotic haptic perception system. Finally, we have ad dressed the issues of how these two subsystems interact dur ing active exploration and how the information from each is integrated. The work described has been implemented and tested on a robot system consisting of a combination tactile array/force-torque sensor, a PUMA robot arm, a pair of CCD cameras, and a Vax 750.
Concurrent Programming and Robotics
Authors: Cox Ingemar J. , Gehani Narain H.
Published: March 2007

Many current robot systems exhibit a significant degree of concurrency, doing many activities in parallel. Future sensor- based robots are expected to exhibit even more concurrency. Programs to control such robots are characterized by the need to wait for external events and/or handle interrupts, deal with concurrent activities, synchronize actions with external events, and communicate with other robots and processes. In this paper, we focus on the advantages of concurrent pro gramming for robotics and suggest that a general-purpose language with the right facilities is a good vehicle for robot programming. In this context we will discuss Concurrent C, an upward-compatible extension of the C language that provides high-level concurrent programming facilities. We give an historical perspective of concurrent programming followed by a brief description of Concurrent C and how Concurrent C programs communicate with robots and de vices. We show by examples how Concurrent C simplifies writing robot programs. Of specific interest are the process interaction and related interrupt handling facilities. We conclude that high-level concurrent programming facilities provide significant advantages for robot programming. In particular, transaction facilities provide an elegant means by which to synchronize with external events and communicate with interacting robots and manufacturing processes. Inter rupts may also be mapped to high-level transaction calls within the language. A concurrent programming language provides a framework in which to describe and develop con current solutions and can hide many details associated with distributed processing from the user. Finally, we believe that a high-level concurrent programming language such as Con current C is not only useful for robotics but also for manufac turing processes in general.
On the Use of Dual- Matrix Exponentials in Robotic Kinematics
Authors: Pradeep A.K. , Yoder Paul J. , Mukundan Rangaswamy
Published: March 2007

This paper sets forth an approach to robotic kinematics that brings together the use of matrix exponentiation and dual numbers. Working from first principles, it is shown that a screw displacement can be represented by the exponential of a dual skew-symmetric matrix; a product of two such matri ces will suffice to specify the relationship between a pair of link coordinate frames. An example problem, dealing with the kinematics of the Rhino XR-2, illustrates how the approach immediately identifies those groups of joint variables that tend to cluster together.
Passive Dynamic Walking
Authors: McGeer Tad
Published: March 2007

There exists a class of two-legged machines for which walking is a natural dynamic mode. Once started on a shallow slope, a machine of this class will settle into a steady gait quite comparable to human walking, without active control or en ergy input. Interpretation and analysis of the physics are straightforward; the walking cycle, its stability, and its sensi tivity to parameter variations are easily calculated. Experi ments with a test machine verify that the passive walking effect can be readily exploited in practice. The dynamics are most clearly demonstrated by a machine powered only by gravity, but they can be combined easily with active energy input to produce efficient and dextrous walking over a broad range of terrain.
A Quantification of Machine Dexterity Applied to an Assembly Task
Authors: Sturges R.H.
Published: March 2007

This article reviews the need for a quantitative measure of dexterity and considers intuitive notions of dexterity based on the scaling laws of biological systems. Task/manipulator interactions are quantified in the human perspective, and machine dexterity is shown to have parallel measures and limitations. A nondimensional definition of dexterity is pro posed based on the information content of task/effector inter actions. It is shown to provide a quantitative measure be tween different robotic systems that have varying degrees of dexterity and interactions between a specific assembly task being performed. Values for the index of difficulty are shown to vary in the work space, and the loci of maximum dexterity that indicate the most favorable task/effector arrangements are determined. The notion of a set of principal axes of dex terity is defined and located in the task/manipulator work space. The peg-in-hole task is used as an example application of this approach.
Trajectory Planning of Robot Manipulators in Noisy Work Spaces Using Stochastic Automata
Authors: Oommen B. John , Andrade Nicte , Sitharam Iyengar S.
Published: March 2007

We consider the problem of a robot manipulator operating in a noisy work space. The robot is assigned the task of moving fromP i toP f. BecauseP i is its initial position, this position can be known fairly accurately. However, becauseP f is usu ally obtained as a result of a sensing operation, possibly vision sensing, we assume thatP f is noisy. We propose a so lution to achieve the motion that involves a new learning automaton, called the Discretized Linear Reward-Penalty (DLRP) automaton. The strategy we propose does not involve the computation of any inverse kinematics. Alternatively, an automaton is positioned at each joint of the robot, and by processing repeated noisy observations of P f the automata operate in parallel to control the motion of the manipulator.
Parallel Algorithms for Computation of the Manipulator Inertia Matrix
Authors: Amin-Javaheri Masoud , Orin David E.
Published: March 2007

This article presents the development of an O( log2 N) parallel algorithm for the manipulator inertia matrix. It is based on an efficient serial algorithm that uses the composite rigid- body method. Recursive doubling is used to reformulate the linear recurrence equations that are required to compute the diagonal elements of the matrix. It results in O( log2 N) levels of computation. Computation of the off-diagonal ele ments involves N linear recurrences of varying size, and a new method, which avoids redundant computation of position and orientation transforms for the manipulator, is developed. The O( log2 N) algorithm is presented in both equation and graphic forms that clearly show the parallelism inherent in the algorithm. The relationship between the number of pro cessors required and the order of the computation is also given for several versions of parallel algorithms for the inertia matrix.