bluuebunny/crossref_metadata_2025 huggingface dataset:
Ambulatory Blood Pressure Monitoring and Diagnostic Errors in Hypertension
Authors: Mar Javier , Pastor Roberto , Abasolo Rosa , De Gauna Ramón Ruiz
Published: March 2007

Random variability of blood pressure complicates the diagnosis and subsequent treat ment of hypertension. To evaluate the importance of the number of blood pressure measurements in the correct diagnosis and control of hypertension, the authors used a Bayesian model to estimate the true average blood pressure of a group of newly diagnosed hypertensives, then calculated the diagnostic error that would result from monitoring methods using 24 daytime measurements or from using only three random monitoring measurements. The study population consisted of 129 individuals with newly diagnosed mild hypertension according to standard criteria, who were also eval uated with an ambulatory blood pressure monitor. In true normotensives (daytime di astolic blood pressure <90 mm Hg), the negative predictive value with three measure ments was 0.92, and it rose to 0.96 with monitoring methods. In mild hypertensives (90-104 mm Hg), the positive predictive value was 0.64 with three measurements and 0.84 with monitonng methods, thus reducing the rate of false mild hypertensives from 35% to 15%. Finally, in patients with moderate or severe hypertension (>104 mm Hg), the positive predictive value improved from 0.26 with three readings to 0.61 with mon itoring methods. Similar results were observed with daytime systolic pressure mea surements. As the number of measurements increased, the diagnostic error due to the random variability of blood pressure became progressively smaller. In cases of hyper tension, the large improvement in predictive values may justify using monitoring meth ods to confirm standard diagnosis. Key words: ambulatory blood pressure monitoring; Bayesian analysis; blood pressure; diagnostic error; hypertension; random variability. (Med Decis Making 1998;18:429-435)
A Bayesian Approach to a General Regression Model for ROC Curves
Authors: Hellmich Martin , Abrams Keith R. , Jones David R. , Lambert Paul C.
Published: March 2007

A fully Bayesian approach to a general nonlinear ordinal regression model for ROC- curve analysis is presented. Samples from the marginal posterior distributions of the model parameters are obtained by a Markov-chain Monte Carlo (MCMC) technique— Gibbs sampling. These samples facilitate the calculation of point estimates and cred ible regions as well as inferences for the associated areas under the ROC curves. The analysis of an example using freely available software shows that the use of nonin formative vague prior distributions for all model parameters yields posterior summary statistics very similar to the conventional maximum-likelihood estimates. Clinically im portant advantages of this Bayesian approach are: the possible inclusion of prior knowl edge and beliefs into the ROC analysis (via the prior distributions), the possible cal culation of the posterior predictive distribution of a future patient outcome, and the potential to address questions such as: "What is the probability that a certain diagnostic test is better in one setting than in another?" Key words: ROC curve; diagnostic test; ordinal regression; Bayesian methods; MCMC; Gibbs sampling; maximum likelihood (Med Decis Making 1998;18:436-443)
Patient or Physician Preferences for Decision Analysis
Authors: Heckerling Paul S. , Verp Marion S. , Albert Nancy
Published: March 2007

The choice between amniocentesis and chononic villus sampling for prenatal genetic testing involves tradeoffs of the benefits and risks of the tests. Decision analysis is a method of explicitly weighing such tradeoffs. The authors examined the relationship between prenatal test choices made by patients and the choices prescribed by deci sion-analytic models based on their preferences, and separate models based on the preferences of their physicians. Preferences were assessed using written scenarios describing prenatal testing outcomes, and were recorded on linear rating scales. After adjustment for sociodemographic and obstetric confounders, test choice was signifi cantly associated with the choice of decision models based on patient preferences (odds ratio 4.44; CI, 2.53 to 7.78), but not with the choice of models based on the preferences of the physicians (odds ratio 1.60; CI, 0.79 to 3.26). Agreement between decision analyses based on patient preferences and on physician preferences was little better than chance (kappa = 0.085 ± 0.063). These results were robust both to changes in the decision-analytic probabilities and to changes in the model structure itself to simulate non-expected utility decision rules. The authors conclude that patient but not physician preferences, incorporated in decision models, correspond to the choice of amniocentesis or chorionic villus sampling made by the patient. Nevertheless, because patient preferences were assessed after referral for genetic testing, prospec tive preference-assessment studies will be necessary to confirm this association. Key words: decision analysis; patient preferences; physician preferences; prenatal genetic testing. (Med Decis Making 1999;19:66-77)
Holistic versus Composite Preferences for Lifetime Treatment Sequences for Type 2 Diabetes
Authors: Mackeigan Linda D. , O'Brien Bernie J. , Oh Paul I.
Published: March 2007

This study of patient preferences for lifetime treatment sequences for type 2 diabetes had three objectives: to assess the feasibility of obtaining holistic preference assess ments using the time-tradeoff (TTO) technique; to compare composite and holistic preference scores for the same lifetime treatment paths; and to assess the validity of composite and holistic preference measures in terms of their congruence with an in dividual's rank-order preferences. 101 persons with type 2 diabetes provided prefer ence ratings for hyperglycemic treatments lasting 30 years, including eight discrete treatment states and four treatment paths. Scenarios described drug and glucose- testing regimens, efficacy of glucose control, and side effects. After ranking and rating scenarios on a thermometer scale, subjects provided TTO preferences for each treat ment state or path scenario. Holistic assessment of treatment paths was feasible with the TTO technique, in terms of useable data (88% of interviews) and effect on coef ficients of variation. Holistic and composite preference scores were not statistically different. Agreement was poor between rankings implied by holistic and composite scores and direct rankings. The authors conclude that lifetime treatment paths with minor differences in health effects can be assessed using either composite (QALY) or holistic (HYE) measures. The validity of these TTO-based preference measures re mains unknown. Key words: individual preferences; diabetes; treatment paths; QALYs. (Med Decis Making 1999;19:113-121)
Subjective Health Status and Health Values in the General Population
Authors: Shmueli Amir
Published: March 2007

Objective. To explore the relationship between rating-scale evaluation of health-related quality of life ("health value") and two subjective evaluations of health: the SF-36 profile and the five-category perception of general health (excellent, very good, good, fair, and poor). Methods. This relationship was explored by linear and nonlinear regression analysis of data obtained through face-to-face interviews with a sample of 2,030 per sons aged 45-75 years representing the Israeli Jewish urban population in that age group. Results. The main outcome is a mapping assigning health values to the sub jective health-status scores, e.g., "good" general health is equivalent to a health value of 76-81, depending on the functional form of the relation. "Poor" health is equivalent to a value of 45-61. The R2 is about 0.3. While the eight scales of the SF-36 were found to be linearly related to health value (R2 = 0.51), the two summary measures— physical component scale (PCS) and mental component scale (MCS)—were not. The scales measuring general health, vitality, and physical functioning were the main de terminants of health value, while the role-performance scales were insignificant. The PCS had a larger effect than the MCS. Discussion. These relationships provide deeper insight into the structure and meaning of the two health-status measures in the general population. They also place earlier determinations of these relationships among sick persons in a broader context and raise several further questions regarding the rela tionship between health values and health status. Key words: rating scale; health- related quality of life; health value; MOS SF-36; subjective evaluation of health; Box- Cox regression. (Med Decis Making 1999;19:122-127)
Women's Perceptions of Breast Cancer Risk
Authors: Woloshin Steven , Schwartz Lisa M. , Black William C. , Welch H. Gilbert
Published: March 2007

Background. Some studies suggest that women dramatically overestimate the risk of having breast cancer while others conclude that they underestimate it. To understand better how women perceive the chance of getting breast cancer, the authors asked women to estimate the risk in several ways. Each woman's answer was related to her actual risk. Methods. Women were randomly selected from a registry of female vet erans in New England. A mailed questionnaire asked each woman to estimate her ten-year risk of dying from breast cancer as a number out of 1,000 ("___ in 1,000" perceived risk) and whether this risk was higher than, the same as, or lower than that of an average woman her age (comparative perceived risk). The woman was also asked to compare her risk of dying from breast cancer with her risk of dying from heart disease. Risk-factor data were collected so that each woman's actual risk of breast cancer death could be estimated (actual risk). Results . 201 women had complete data. The median age of the respondents was 62 years (range 27-80), and 98% were high school graduates. Most women (98%) overestimated the "___ in 1,000" risk of breast cancer death—half by eightfold or more (Interquartile range, 4-36-fold overestimates). In contrast, only 10% of these women thought that they were at higher risk than an average woman their age. Most correctly thought that their risk of dying from breast cancer was lower than their risk of dying from heart disease. The women's "___ in 1,000" perceived risks of breast cancer death were unrelated to their actual risks and had no significant agreement with an external bench mark of importantly "high risk" (i.e., met risk criteria for the Tamoxifen primary pre vention trial). In contrast, the women's comparative perceptions of being at low, av erage or high risk were related to actual risks and significantly agreed with the "high risk" benchmark. Most women not at importantly "high risk" correctly classified them selves ; however, almost two thirds of "high risk" women misclassified themselves as "average or lower than average risk." Conclusions. The method used to elicit percep tions of risk matters. These women's responses to the comparative questions showed that they "knew more" about their actual risks than their open-ended numeric re sponses suggested. Key words: risk; perception; decision making; breast neoplasms. (Med Decis Making 1999;19:221-229)
A Comparison of Preference Assessment Instruments Used in a Clinical Trial
Authors: Glick Henry A. , Polsky Daniel , Willke Richard J. , Schulman Kevin A.
Published: March 2007

Objectives. To compare preference assessments that were made by using the EuroQol EQ-5D and the Health Utilities Index Mark II. Subjects. 561 patients in a randomized trial of tirilazad mesylate for aneurysmal subarachnoid hemorrhage. Measures . Three preference assessments (a value score for the EuroQol instrument and value and utility scores for the Health Utilities Index) made three months after randomization. The av erages for each of the three scores, stratified by clinical outcomes and attributes of the Health Utilities Index health status classification system, were compared. To eval uate potential sources of difference between the instruments, the authors estimated two alternative Health Utilities Index sconng rules that were based on patient re sponses to the EuroQol instrument. Results . Patients' ratings of their current health made by using the 100-point visual analog scale from the EuroQol instrument were more similar to the utility scores for the Health Utilities Index than they were to the value scores for the Health Utilities Index. The biggest differences between the visual analog scores for the EuroQol instrument and the utility scores for the Health Utilities index were seen at higher levels of functioning. Conclusion. For states representing higher levels of functioning, differences were seen between patients' self-ratings ob tained by using the EuroQol instrument and the patients' utility scores on the Health Utilities Index; for states representing lower levels of functioning, substantial agreement was observed between these two scores. Differences observed at the higher levels of functioning suggest that further research is needed to determine whether the Health Utility Index's assignment of a score of 1.0 to the reference state representing being healthy is appropriate. Key words: preference assessment; health utilities index; EuroQol; clinical trials; subarachnoid hemorrhage. (Med Decis Making 1999; 19:265- 275)
Are More Options Always Better?
Authors: Schwartz Janet A. , Chapman Gretchen B.
Published: March 2007

Consumer choice research has shown that, contrary to normative theory, the intro duction of an inferior alternative to an existing choice set can increase the likelihood that one of the original alternatives will be chosen. This phenomenon, the attraction effect, is relevant to physician decision making, particularly when the physician is in the role of a consumer who must make decisions about prescribing medications when a number of alternatives are available. To investigate the attraction effect in physician decision making, 40 internal medicine residents reviewed three patient cases (con cerning depression, sinusitis, and vaginitis) and then chose the most appropriate med ication for each patient. In some versions of the cases, two medication options were available. Other versions included a third medication (the decoy) that was inferior in every way to one of the original options (the target) but not to the other (the competitor). The results showed that addition of the "decoy" medication increased the likelihood of choosing the target medication. That is, the attraction effect does occur in physicians' decisions about medications. Physicians should be aware of this bias when evaluating or suggesting several similarly attractive medications or treatment options for the same medical condition. Key words: attraction effect; decision making; physicians' decisions; consumer choice. (Med Decis Making 1999; 19:315-323)
Health Values and Prospect Theory
Authors: Treadwell Jonathan R. , Lenert Leslie A.
Published: March 2007

Health values are important components of medical decisions. Experimental data sug gest that people value health in complex and dynamic ways. Prospect theory is a descriptive theory of choice that may accurately characterize how people assign values to health states. The authors first provide background on prospect theory and how it can be applied to health values. Next, they review the relevant health research and find mixed support for prospect theory. Last, they discuss implications of prospect theory for cost-effectiveness analysis. The application of prospect theory to health deserves further research because it may help clarify the link between health and values. Key words: health values; prospect theory; utility theory; quality of life; patient preferences; decision analysis; cost-effectiveness analysis. (Med Decis Making 1999; 19: 344-352)
Probabilistic Sensitivity Analysis Incorporating the Bootstrap
Authors: Pasta David J. , Taylor Jennifer L. , Henning James M.
Published: March 2007

Decision-analytic models are frequently used to evaluate the relative costs and benefits of alternative therapeutic strategies for health care. Various types of sensitivity analysis are used to evaluate the uncertainty inherent in the models. Although probabilistic sensitivity analysis is more difficult theoretically and computationally, the results can be much more powerful and useful than deterministic sensitivity analysis. The authors show how a Monte Carlo simulation can be implemented using standard software to perform a probabilistic sensitivity analysis incorporating the bootstrap. The method is applied to a decision-analytic model evaluating the cost-effectiveness of Helicobacter pylori eradication. The necessary steps are straightforward and are described in detail. The use of the bootstrap avoids certain difficulties encountered with theoretical distri butions. The probabilistic sensitivity analysis provided insights into the decision-analytic model beyond the traditional base-case and deterministic sensitivity analyses and should become the standard method for assessing sensitivity. Key words: decision analysis; sensitivity analysis; decision trees; bootstrap; Monte Carlo; cost-effective ness ; sampling. (Med Decis Making 1999; 19:353-363)
Motivating Mammography Adherence in Elderly Latinas
Authors: Veit Clairice T.
Published: March 2007

Many elderly Latinas do not have mammography every one to two years as recom mended by cancer organizations. To elucidate the causal factors underlying this be havior, 52 Latinas, aged 65 and over, were asked to judge the likelihood of having yearly mammography in 79 different scenanos constructed from factor levels of cost, perceived risk, and the source of a recommendation (none, a recognized cancer or ganization, a doctor), assuming a convenient mammography facility. A configural- weight-averaging model, with different parameter values for the 30 adherers (women who reported having had mammography at least twice in the preceding four years) and the 22 non-adherers, gave a good fit to the data and did well in predicting reported mammography adherence (r = 0.85). According to this model, offering free mammog raphy would not induce non-adherers to adhere; they would require a recommendation, and value a doctor's as highly as that of a recognized cancer organization, but reported never having received one from either source. All 52 women reported never receiving risk information from any source. These results have direct educational and dissemi nation implications for cancer organizations. Key words: breast cancer screening; screening barriers; testing decision models; elderly Latinas. (Med Decis Making 1999; 19:448-465)
Assessing Convergent Validity of Health-state Utilities Obtained Using Different Scaling Methods
Authors: Nickerson Carol A.E.
Published: March 2007

A number of empirical studies have attempted to assess the convergent validity of health-state utilities obtained using two or more scaling methods (standard gamble, time tradeoff, rating scale, magnitude estimation, equivalence technique, and willing ness-to-pay). The data from these studies can be mapped onto an N x K matrix, where N and K are the numbers of respondents and health states, respectively, and each matrix cell consists of a pair of health-state utilities, one obtained using scaling method X and the other obtained using scaling method Y. The Pearson's r assessing convergent validity can then be computed as 1) the unraveled correlation over all N x K data pairs, 2) the mean within-respondent correlation, 3) the mean within-health- state correlation, or 4) the correlation of the across-respondents means. These four different ways of computing the correlation do not necessarily yield the same results. The appropriateness of each method of computing the correlation is considered. Key words: convergent validity; equivalence technique; health-state preferences; health- state utilities; magnitude estimation; person tradeoff; rating scale; scaling; standard gamble; time tradeoff; willingness-to-pay. (Med Decis Making 1999;19:487-496)
Sensitivity Analysis on a Chance Node with More Than Two Branches
Authors: Sendi Peter P. , Clemen Robert T.
Published: March 2007

Sensitivity analysis is an essential part of decision analysis. The literature on medical decision analysis suggests the use of two-branch chance nodes in decision trees to avoid logical inconsistencies during sensitivity analysis. The authors show that the two- branch decomposition is not appropriate for sensitivity analysis when multiple out comes from a single state cannot be disentangled into a sensible sequence of events. They recommend retaining the natural structure of the tree and propose two sensitivity- analysis methods for use on chance nodes with three or more branches. Key words: sensitivity analysis; decision analysis; decision tree; probability. (Med Decis Making 1999;19:499-502)
Use of a Multiprocessor for Control of a Robotic System
Authors: Klein Charles A. , Wahawisan Weerakiat
Published: March 2007

In the control of robotic systems, multiprocessors have a number of potential advantages over single-processor configurations. These advantages include the possibility of modular future expansion, increased speed, and fault tolerance. This paper describes both the hardware and software design of a multiprocessor system and its use in controlling the OSU Hexapod vehicle, a complex robotic system.

With the design of an inexpensive, high-density, eight-channel parallel line unit (PLU), it is possible to link five LSI-11 processors in a fully connected configuration. This configuration is very valuable for experimentation, since trials of tree, star, and loop structures can be made by simply ignoring links that are not needed. First, a tree structure is used to implement a hierarchical control algorithm run on a previously used uniprocessor system. Next, fault-tolerant features are added so that failed units are automatically replaced by spare units or, if all spares are in use, the necessary tasks are covered by the central processor, with a decrease in servoing frequency. To decentralize control to improve overall reliability, a ring structure is also used. If a processor fails, the ring is automatically reconfigured to isolate the faulty unit. Another application for the multiprocessor in the control of the OSU Hexapod vehicle is for real-time optimization of leg tip forces. This task demonstrates the usefulness of the multiprocessor in a task that is not strictly parallel in form.
On the Equivalence of Lagrangian and Newton-Euler Dynamics for Manipulators
Authors: Silver William M.
Published: March 2007

Recently, there has been considerable interest in efficient formulations of manipulator dynamics. The inefficiency of the classic Lagrangian formulation is well known, leading several researchers to a new formulation based on the Newton-Euler equations. This formulation is highly ef ficient, but there may be some confusion as to the source of this efficiency. This paper shows that there is in fact no fundamental difference in computational efficiency between Lagrangian and Newton-Euler formulations. The efficiency of the above-mentioned Newton-Euler formula tion is due to two factors: the recursive structure of the computation and the representation chosen for the rota tional dynamics. Both of these factors can be achieved in a Lagrangian formulation. Recursive Lagrangian dy namics has been discussed previously by Hollerbach. This paper compares the representations that have been used and shows that with a proper choice the Lagrangian formulation is indeed equivalent to the Newton-Euler formulation.
AML/V : An Industrial Machine Vision Programming System
Authors: Lavin M.A. , Lieberman L.I.
Published: March 2007

The use of robots rather than human workers to perform industrial tasks has a number of disadvantages. One is that parts and tools must be presented to the robot at ac curate positions and orientations. Another is that robots cannot do implicit in-process inspection the way people do. These two disadvantages can be reduced through the use of machine vision to determine the position, orienta tion, and even identity of parts and tools in the workspace and to look for qualitative and quantitative defects. This paper describes AML/V, an experimental hardware and software extension of an existing robot programming sys tem, intended for industrial machine vision programming.
Development of an Optical Distance Sensor for Robots
Authors: Okada Tokuji
Published: March 2007

A description is given of the development of an optical distance sensor for robots. The surface of an object is illuminated by light coming through a pinhole, and the light reffected on the surface is guided into a photosensor array by another pinhole. Based on the position of the photosensor unit that detects a magnitude greater than that detected by any other unit, the distance between the surface and the sensor head is determined geometrically, without influence from circumferential illumination or other conditions of an object such as irregularity, reflectivity, and orientation. This sensor is quite powerful and should have a wide variety of practical uses. Both analytic and experimental results are presented.
One Robust, Dynamic Control Algorithm for Manipulation Systems
Authors: Cvetković Vesna , Vukobratović Miomir
Published: March 2007

By digital simulation of an elementary functional movement for the manipulation system with six rotational degrees of freedom, a few dynamic control algorithms are investigated. The basic control structure consists of program (nominal) control and compensating term, which should provide for nominal trajectory tracking under initial-condition perturbations. As compensating control in the stage of perturbed regimes, the following were observed: (1) decentralized control, that is, local linear control law on the each actuator subsystem level; (2) suboptimal control, where the linear term is the same as local control, but "global" term takes into consideration the disturbance acting upon the subsystem as the result of coupling with other subsystems; (3) control law consisting of linear local control and nonlinear compensator, synthesized using Liapunov's second method. Those control laws are compared with respect to stability, tracking, energy consumption, and computational efficiency.
Use of Force and Attitude Sensors for Locomotion of a Legged Vehicle over Irregular Terrain
Authors: Klein Charles A. , Olson Karl W. , Pugh Dennis R.
Published: March 2007

A number of legged vehicles are being developed for their mobility characteristics over irregular terrain. One such vehicle is The Ohio State University Hexapod vehicle ( OSU Hexapod) . Recently, the vehicle has been modified so that it can successfully walk over uneven terrain. Each of the feet has been equipped with two semiconductor strain gauges to measure lateral forces and a piezoelectric load cell to measure vertical forces. A vertical gyroscope and pendulums for orientation sensing have also been added.

The control of locomotion over rough terrain can be decomposed into two complementary control processes, attitude control and active compliance. Attitude control is used to maintain the body tilt in a desired orientation, and active compliance is used to provide a suspension system by distributing force loading among the legs. It has been found that optimal force setpoints for the active-compliance algorithm can be calculated in closed form.

This paper discusses the sensing hardware and the control system needed for legged locomotion over irregular terrain. Experimental results are provided for both statically determinate and indeterminate hexapod gaits.
Footprints in the Asphalt
Authors: Sutherland Ivan E. , Ullner Michael K.
Published: March 2007

This paper describes our experiences with a man-carrying, 1600-lb, gasoline-powered, hydraulically actuated, six-legged walking machine. An on-board computer uses leg position and loading information to select one of a few possible hy draulic connections of the leg actuators by switching direc tional control valves. Passive parallel connections of hydraulic actuators distribute loads equally among several legs, creat ing the effect of a smaller number of "virtual legs. " Series connections of hydraulic actuators achieve coordinated leg motions during walking. The machine uses no sophisticated servos.
Dynamic Walk of a Biped
Authors: Miura Hirofumi , Shimoyama Isao
Published: March 2007

The authors have developed five kinds of biped locomotive robots so far. They are named BIPER-1, 2, 3, 4, and 5. All of them are statically unstable but can perform a dynamically stable walk with suitable control. BIPER-1 and BIPER-2 walk only sideways. BIPER-3 is a stilt-type robot whose foot contacts occur at a point and who can walk sideways, back ward, and forward. BIPER-4's legs have the same degrees of freedom as human legs. BIPER-5 is similar to BIPER-3, but in the case of BIPER-5 all apparatus, such as the computer, are mounted on it.

This paper deals with the control theory used for BIPER-3 and BIPER-4. In both cases, basically the same control method is applied. The most important point is that the mo tion of either robot during the single-leg support phase can be approximated by the motion of an inverted pendulum. Ac cordingly, in this paper, dynamic walk is considered to be a series of inverted-pendulum motions with appropriate condi tions of connection.
A Study of Design and Control of a Quadruped Walking Vehicle
Authors: Hirose Shigeo
Published: March 2007

The paper addresses some of the fundamental problems of energy efficiency, design, and adaptive gait control of quadru ped walking vehicles. The design principle of a leg called a gravitationally decoupled actuator ( GDA) is shown to be indispensable for realizing energetically efficient walking mo tion. A novel mechanism, the three-dimensional Cartesian- coordinate pantograph ( PANTOMEC), which follows the GDA principle and has a lightweight structure, is introduced. A constructed quadruped walking vehicle model is then de scribed : the walking vehicle has the PANTOMEC leg mecha nisms, eight tactile sensors and a posture detector, and is hierarchically controlled by a microcomputer. Comparatively high energy efficiency and a certain degree of terrain adapt ability is demonstrated. It is thus shown that a practical walking vehicle can be designed using the proposed method.

The adaptive gait control problem is formalized, and an algorithm for terrain-adaptive gait control is presented. By computer simulation, it is shown that the algorithm produces an efficient gait while avoiding "deadlock" positions in nego tiating terrain. The algorithm is shown to be applicable for the control of future quadruped walking vehicles with visual sensors.
An Approach to the Use of Terrain- Preview Information in Rough-Terrain Locomotion by a Hexapod Walking Machine
Authors: Ozguner F. , Tsai S.J. , McGhee R.B.
Published: March 2007

Until the present time, experiments with computer-controlled walking machines have generally not made use of terrain- preview information. This paper presents the results of exper iments with a laboratory-scale hexapod walking machine furnished with a triangulation ranging system making use of two charge-injection-device ( CID) television cameras and a hand-held laser. The operator uses the laser to designate candidate footholds, which are accepted or rejected automati cally by the machine. Accepted footholds guide the machine over rough terrain with very little disturbance to body atti tude. This semiautomatic system represents a step toward the eventual realization of a fully automatic system. The paper includes a description of both hardware and software, and presents experimental results verifying the practicality of the approach.
Model-Based Recognition and Localization from Sparse Range or Tactile Data
Authors: Grimson W. Eric L. , Lozano-Pérez Tomás
Published: March 2007

This paper discusses how local measurements of three- dimensional positions and surface normals ( recorded by a set of tactile sensors, or by three-dimensional range sensors), may be used to identify and locate objects from among a set of known objects. The objects are modeled as polyhedra having up to six degrees of freedom relative to the sensors. We show that inconsistent hypotheses about pairings between sensed points and object surfaces can be discarded efficiently by using local constraints on distances between faces, angles between face normals, and angles (relative to the surface normals) of vectors between sensed points. We show by simu lation and by mathematical bounds that the number of hy potheses consistent with these constraints is small. We also show how to recover the position and orientation of the object from the sensory data. The algorithm's performance on data obtained from a triangulation range sensor is illustrated.
An Approach to Automatic Robot Programming Based on Inductive Learning
Authors: Dufay Bruno , Latombe Jean-Claude
Published: March 2007

Automatic programming of manipulator robots attracts in creasing interest within the context of mechanical assembly. In this paper we focus on the problem of mating two parts, which requires sensor-based strategies to deal with geometric uncertainty. We present a system that embodies a two-phase approach to build robot programs implementing such strate gies. First a training phase interacts with the robot actuatorsand sensors and produces traces of execution of a given part- mating operation. Next a purely computational induction phase transforms these traces into an executable manipula tor-level program for the operation. The system embedding this approach has been completely implemented, and it has been used experimentally on several assembly tasks.
Strategies for Solving Collision-free Trajectories Problems for Mobile and Manipulator Robots
Authors: Gouzènes Laurent
Published: March 2007

This article addresses issues involved in programming auto matic solvers for collision-avoidance problems in robotics. It presents a refined notion of empty space and shows that solution methods to the find-path problem all reduce to graph-search techniques. The article introduces an intrinsic tree structure for empty space that reduces the complexity of the problem and discusses inherent limitations to implemen tations, taking into account approximation and computer geometry problems. Computational complexity and practical limitations of the methods are addressed. This study shows how to develop a very simple and efficient solution to prob lems of gross motion for general manipulator robots. The approach is compatible with arbitrary assumptions about ob stacle geometry and representation of real objects in a com puter.
Using the Gaussian Image to Find the Orientation of Objects
Authors: Brou Philippe
Published: March 2007

Current three-dimensional vision algorithms can generate depth maps or vector maps from images, but few algorithms extract high-level information from these depth maps. This paper identifies one algorithm that determines an object's orientation by matching object models to depth map data. The object models are constructed by mapping surface orien tation data onto spheres. This process is based on a mathe matical theorem that can be applied only to convex objects, but some extensions for nonconvex objects are presented. The paper shows that a global approach can be used successfully in cases where objects do not touch one another. Another important result illustrates the size of the space of rotations. It shows that even when 6,000 rotations are almost uniformly distributed for matching, errors of 17 degrees are still possible.
Parallelism in Manipulator Dynamics
Authors: Lathrop Richard Harold
Published: March 2007

This paper addresses the problem of efficiently computing the motor torques required to drive a manipulator arm in free motion, given the desired trajectory—that is the inverse dynamics problem. It analyzes the high degree of parallelism inherent in the computations and presents two "mathemati cally exact "formulations especially suited to high-speed, highly parallel implementations using VLSI devices. The first method presented is a parallel version of the recent linear Newton-Euler recursive algorithm. The time cost is linear in the number of joints, but the real-time coefficients are re duced by almost two orders of magnitude. The second formu lation reports a new parallel algorithm that shows that it is possible to improve on the linear time dependency. The real time required to perform the calculations increases only as the [ log2] of the number of joints. Either formulation is sus ceptible to a systolic pipelined architecture in which complete sets of joint torques emerge at successive intervals of four floating-point operations. Hardware requirements necessary to support the algorithm are not excessive, and a VLSI im plementation architecture is possible.
Motion of Objects in Contact
Authors: Hopcroft John , Wilfong Gordon
Published: March 2007

The use of computers in the design, manufacture, and ma nipulation of physical objects is increasing. An important aspect of reasoning about such actions concerns the motion of objects in contact. The study of problems of this nature requires not only the ability to represent physical objects but also the development of a framework or theory in which to reason about them. In this paper such a development is in vestigated and a fundamental theorem concerning the motion of objects in contact is proved. The simplest form of this theorem states that if two objects in contact can be moved to another configuration in which they are in contact, then there is a way to move them from the first configuration to the second configuration such that the objects remain in contact throughout the motion. This result is proved when translation and rotation of objects are allowed. The problem of more generalized types of motion is also discussed. This study has obvious applications in compliant motion and in motion planning.
Implementation of Force Feedback in Manipulation Robots
Authors: Stokic Dragan , vnkobratovic Miomir , Hristic Dragan
Published: March 2007

This paper presents the experimental results of implementing force feedback in controlling a robotic system. We developed an experimental gripper with force transducers that measure all three components of the forces in contact points between the payload and gripper. A direct digital controller is devel oped for a particular robotic system that includes force feed back from the transducers on the gripper. The force feedback is intended to improve both the so-called "gross motion " and "fine motion" control. In the first case, the feedback by dy namic force improves the quality of tracking fast trajectories and makes the controller robust to variation of the parame ters of the payload. In the second case, the force feedback has to reduce reaction forces appearing in the "peg-in-hole" process between the parts being mated. The experimental results show the benefits obtained by force feedback imple mentation in both cases. This is proof that force feedback can be used successfully for general control of robots for various types of tasks.
Kinematic Analysis of Manipulators Using the Zero Reference Position Description
Authors: Gupta K.C.
Published: March 2007

This paper presents a new method ofkinematic analysis of manipulators, called the zero reference position method. In this method, the description of the manipulator is in terms of the axes directions and locations in the zero reference posi tion. This position is a conveniently chosen position in which all joint variable values are defined to be zero. This type of manipulator description is easy to learn and is not prone to errors of interpretation. The governing kinematic equations of the manipulator are derived from the principle of similarity. In this paper, it is shown that this method leads to a modular approach to the closed-form solutions of manipulators with ordinary or geared three-roll wrists. Complete solutions for six types of contemporary industrial robots are included.
Kinematics Simulation of Serial Manipulators
Authors: Paul B. , Rosa J.
Published: March 2007

This paper presents a systematic development for finding position, velocity, and acceleration of one or more points of interest on one or more links of a serial manipulator. The system of equations given is well suited for direct kinematics and effectively supplies the influence coefficients or velocity Jacobians needed for a subsequent dynamics or kinetostatics simulation. An alternative to the Denavit-Hartenberg matri ces is suggested, and a direct vector statics solution for actua torforces and torques is provided. It is shown that all veloci ties and accelerations (linear and angular) are simply expressed in terms of certain so-called star matrices. By exploiting the skew symmetry of these matrices as well as sparseness properties wherever possible, it is shown that the arithmetic operation counts can be reduced significantly in the calculations. The ideas presented here have been imple mented in a computer program that was used to partially verify the practicality and efficiency of the techniques devel oped.
Computationally Efficient Kinematics for Manipulators with Spherical Wrists Based on the Homogeneous Transformation Representation
Authors: Paul Richard P. , Hong Zhang
Published: March 2007

Most manipulators in use today are kinematically simple, and closed-form symbolic equations are the most efficient means of expressing their kinematics. The analysis presented in this paper is based on the use of homogeneous transforma tions to describe position and orientation. Using these methods, kinematic equations are obtained directly in a form suitable for computer implementation. The equations are numerically stable and are obtained almost automatically. The resulting equations involve the minimum number of mathematical operations.
The Canonical Inverse Velocity and Acceleration Solutions of a Planar Two-Link Open Chain
Authors: Stanišić M.M. , Pennock G.R.
Published: March 2007

This paper describes the instantaneous kinematics of the terminal link of a planar two-link open chain using the ca nonical coordinate system of planar two-parameter motion. The first- and second-order instantaneous invariants of the motion of the terminal link are presented. Using a systematic procedure, the results are applied to the inverse velocity and acceleration problems of a two-link open chain. The solutions to the inverse kinematic problems are important, for exam ple, in a robot positioning mechanism. Two examples are presented, a revolute-revolute robot positioner and a pris matic-revolute robot positioner.
Geometric Optimization of Serial Chain Manipulator Structures for Working Volume and Dexterity
Authors: Vijaykumar R. , Waldron K.J. , Tsai M.J.
Published: March 2007

Broadly speaking, the regional structure of a manipulator, which consists of the three inboard joints and their associated members, determines the workspace shape and volume.

The orientation structure, which for a six-degrees-of-free dom manipulator consists of the three outboardjoints and members, determines the geometric dexterity or orientation potential of the manipulator. It is possible to determine the optimal dimensions of the regional structure for a given total length, using straightforward geometric arguments. By the use of the spherical counterpart of Grashof's theorem formu lated by Freudenstein (1964-65), it is also possible to show that there is an optimum geometry of the orientation structure.

Two methods of characterizing geometric dexterity are utilized in this paper. The first is the concept of a dexterous workspace, which is a portion of the workspace within which the hand may assume any orientation. Although the dex terous workspace is a very useful concept for theoretical purposes, it is of limited practical utility because mechanical joint motion limits usually preclude its existence in real industrial robot structures. The second method of character izing geometric dexterity is to trace the portion of the work space within which the hand can assume a specified orienta tion.

In this paper, the geometric conditions for the existence of a dexterous workspace are formulated for geometrically optimum, six-revolute manipulator structures. The optimiza tion criteria used include,freedom from geometric singular ities. We show that for an optimal geometry, singular posi tions can be completely excluded with small reductions of the joint motion ranges. These reductions have a negligible effect on the geometric performance of the system.
Toward Efficient Trajectory Planning: The Path-Velocity Decomposition
Authors: Kant Kamal , Zucker Steven W.
Published: March 2007

We present a novel approach to solving the trajectory plan ning problem (TPP) in time-varying environments. The es sence of our approach lies in a heuristic but natural decom position of TPP into two subproblems: (1) planning a path to avoid collision with static obstacles and (2) planning the velocity along the path to avoid collision with moving obsta cles. We call thefirst subproblem the path planning problem (PPP) and the second the velocity planning problem (VPP). Thus, our decomposition is summarized by the equation TPP => PPP + VPP. The symbol => indicates that the de composition holds under certain assumptions, e.g., when obstacles are moving independently of ( i.e., not tracking ) the robot. Furthermore, we pose the VPP in path-time space, where time is explicitly represented as an extra dimension, and reduce it to a graph search in this space. In fact, VPP is transformed to a two-dimensional PPP in path-time space with some additional constraints. Algorithms are then pre sented to solve the VPP with different optimality criteria: minimum length in path-time space, and minimum time.
Running With Symmetry
Authors: Raibert Marc H.
Published: March 2007

Symmetry can simplify the control of dynamic legged sys tems. In this paper, the symmetries studied describe motion of the body and legs in terms of even and odd functions of time. A single set of equations describes symmetric running for systems with any number of legs and for a wide range of gaits. Techniques based on symmetry have been used in laboratory experiments to control machines that run on one, two, and four legs. In addition to simplifying the control of legged machines, symmetry may help us to understand legged locomotion in animals. Data from a cat trotting and galloping on a treadmill and from a human running on a track conform reasonably well to the predicted symmetries.
On the Representation and Estimation of Spatial Uncertainty
Authors: Smith Randall C. , Cheeseman Peter
Published: March 2007

This paper describes a general method for estimating the nominal relationship and expected error (covariance) between coordinate frames representing the relative locations of ob jects. The frames may be known only indirectly through a series of spatial relationships, each with its associated error, arising from diverse causes, including positioning errors, measurement errors, or tolerances in part dimensions. This estimation method can be used to answer such questions as whether a camera attached to a robot is likely to have a particular reference object in its field of view. The calculated estimates agree well with those from an independent Monte Carlo simulation. The method makes it possible to decide in advance whether an uncertain relationship is known accu rately enough for some task and, if not, how much of an improvement in locational knowledge a proposed sensor will provide. The method presented can be generalized to six degrees offreedom and provides a practical means of esti mating the relationships ( position and orientation) among objects, as well as estimating the uncertainty associated with the relationships.