bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensor-Based Exploration: Incremental Construction of the Hierarchical Generalized Voronoi Graph
Authors: Choset Howie , Walker Sean , Eiamsa-Ard Kunnayut , Burdick Joel
Published: December 2004

This paper prescribes an incremental procedure to construct roadmaps of unknown environments. Recall that a roadmap is a geometric structure that a robot uses to plan a path between two points in an environment. If the robot knows the roadmap, then it knows the environment. Likewise, if the robot constructs the roadmap, then it has effectively explored the environment. This paper focuses on the hierarchical generalized Voronoi graph (HGVG), detailed in the companion paper in this issue. The incremental construction procedure of the HGVG requires only local distance sensor measurements, and therefore the method can be used as a basis for sensor-based planning algorithms. Simulations and experiments using a mobile robot with ultrasonic sensors verify this approach.
Computing n-Finger Form-Closure Grasps on Polygonal Objects
Authors: Liu Yun-Hui
Published: December 2004

This paper presents an efficient algorithm for computing all n-finger form-closure grasps on a polygonal object based on a new sufficient and necessary condition for form-closure. With this new condition, it is possible to transfer the problem of computing the form-closure grasp in R3 to one in R1. We demonstrate that the non-form-closure grasps consist of two convex polytopes in the space of n parameters representing grasp points on sides of the polygon. The proposed algorithm works efficiently for n ≤ 3 and takes O(n3n/2) time for n > 3, where n denotes the number of the fingers. The algorithm has been implemented and its efficiency has been confirmed with two examples.
Singularity-Consistent Parameterization of Robot Motion and Control
Authors: Nenchev Dragomir N. , Tsumaki Yuichi , Uchiyama Masaru
Published: December 2004

The inverse kinematics problem is formulated as a parameterized autonomous dynamical system problem, and respective analysis is carried out. It is shown that a singular point of work space can be mapped either as a critical or a noncritical point of the autonomous system, depending on the direction of approach to the singular point. Making use of the noncritical mapping, a closed-loop kinematic controller with asymptotic stability and velocity limits along degenerate singular or near-singular paths is designed. The authors introduce a specific type of motion along the reference path, the so-called natural motion. This type of motion is obtained in a straightforward manner from the autonomous dynamical system and always satisfies the motion constraint at a singular point. In the vicinity of the singular point, natural motion slows down the end-effector speed and keeps the joint velocity bounded. Thus, no special trajectory replanning will be required. In addition, the singular manifold can be crossed, if necessary. Further on, it is shown that natural motion constitutes an integrable motion component. The remaining, nonintegrable motion component is shown to be helpful in solving a problem related to the critical point mapping of the autonomous system. The authors design a singularity-consistent resolved acceleration controller, which they then apply to singular or near-singular trajectory tracking under torque limits. Finally, the authors compare the main features of the singularity-consistent method and the damped-least-squares method. It is shown that both methods introduce a so-called algorithmic error in the vicinity of a singular point. The direction of this error is, however, different in each method. This is shown to play an important role for system stability.
Geared Robot Manipulators with a Jointed Unit: Topological Synthesis and Its Application
Authors: Chen Dar-Zen , Huang Yu-Chu , Duh Dong-Wen
Published: December 2004

An efficient and systematic methodology for the topological synthesis of geared robot manipulators (GRMs) with a jointed unit is developed. The approach is based on the idea that the kinematic structure of a GRM with a jointed unit is composed of an equivalent open-loop chain (EOLC), disjointed mechanical transmission lines (MTLs), and jointed MTLs. It is shown that the jointed MTLs can be decomposed as a two-DoF nonfractionated jointed unit and several one-DoF disjointed units, connected in series. The characteristics of the jointed unit are laid out, and admissible jointed units are enumerated from the existing atlas accordingly. A systematic methodology is developed to enumerate admissible GRMs with a jointed unit of preferred DoF and number of links. It is also shown that the concept of jointed MTLs leads to the design of GRMs with decoupled joint motion by proper choices of gear ratios in the drive train.
A Dynamic Vision Algorithm to Locate a Vehicle on a Nonstructured Road
Authors: Aufrère R. , Chapuis R. , Chausse F.
Published: December 2004

In this article, we present a method of nonmarked road following that is based on images coming from an onboard monochromatic camera. The principle is based first on a segmentation stage that makes it possible to locate the road area in the image, managing, if possible, the shadows on the roadway. The method is original since the algorithm must be running day as well as night (infrared camera) so it does not use color images. Furthermore, a single constant threshold is used whatever the analyzed sequence. Then, a localization stage estimates the vehicle’s location on the roadway. The estimate of the parameters L (road width) and α (camera inclination angle) (assumed known and constant for certain existing approaches) ensures a greater robustness of the other estimated parameters. Finally, a filtering stage is applied onto the previous data and predicts the position of the vehicle in the next image. Results are shown for each stage on both a normal nonmarked road and a forest lane sequence. The computational times are very low and will permit a real-time implementation on an experimental vehicle.
Target Representation on an Autonomous Vehicle with Low-Level Sensors
Authors: Bicho Estela , Mallet Pierre , Schöner Gregor
Published: December 2004

How can low-level autonomous robots with only very simple sensor systems be endowed with cognitive capabilities? Specifically, we consider a system that uses seven infrared sensors and five microphones to avoid obstacles and acquire sound targets. The cognitive abilities of the vehicle consist of representing the direction in which a sound source lies. This representation supports target detection, estimation of target direction, selection of one out of multiple-detected targets, storage of target direction in short-term memory, continuous updating of memory, and deletion of memorized target information after a characteristic delay. We show that the dynamic approach (attractor dynamics) employed to control the motion of the robot can be extended to the level of representation by using dynamic neural fields to interpolate sensory information. We show how the system stabilizes decisions in the presence of multivalue sensorial information and activates and deactivates memory. Smooth integration of this target representation with target acquisition, in the form of phonotaxis, and obstacle avoidance is demonstrated.
Resonance-Induced Failure of Entrapment: Application to Industrial Parts Feeding
Authors: Krishnasamy Jayaraman , Jakiela Mark J.
Published: December 2004

Parts feeders are devices used in automated assembly lines to present component parts to the assembly machinery in a consistent and predetermined orientation. The process of converting a randomly oriented set of parts (as obtained from a vendor) into an ordered array is called parts feeding. There are many different types of feeders and feeding techniques used in the industry. This paper deals with a particular feeding process referred to here as vibratory entrapment. It describes a particular cause of failure of vibratory entrapment, namely, resonance. Failure due to resonance was first observed in high-speed video images of the entrapment phenomenon. This paper provides a description of the mechanics of failure of entrapment due to resonance. The mechanics is introduced with the simple example of a ping-pong ball in a cup and extended to real parts in a parts feeder. Conditions for resonance are derived and experimentally verified for a simple part shape and vibration pattern.
Computing Immobilizing Grasps of Polygonal Parts
Authors: van der Stappen A. Frank , Wentink Chantal , Overmars Mark H.
Published: December 2004

We present the first algorithms for computing all placements of (frictionless) point fingers that put a polygonal part in form closure and all placements of point fingers that achieve second-order immobility of a polygonal part. Our algorithms run in O(n2+∈ +K) and O(n2 log2 n + K) time in the case of form closure and second-order immobility, respectively, where n is the number of vertices of the polygon, K is the description size of the resulting set of finger placements, and ∈ is an arbitrarily small constant. The basis of our algorithm is a translation of the problem into geometric searching problems, which are solved using efficient data structures. Our results can be extended to the problem of computing all placements of a line and two points that put a polygonal part in form closure. The resulting algorithm runs in O(n2 log2 n + K) time, where K is again the description size of the output.
Online Suboptimal Obstacle Avoidance
Authors: Shiller Zvi
Published: December 2004

This paper presents an online planner for suboptimal obstacle avoidance. It generates near-shortest paths incrementally by avoiding obstacles optimally one at a time. In known environments, obstacles are avoided in an order determined by a global criterion. In unknown environments, obstacles are avoided as they are detected by on-board sensors. This avoidance strategy is guaranteed to reach the goal regardless of the order in which the obstacles are avoided. The method is demonstrated in several examples for an omnidirectional point robot moving among planar polygonal obstacles.
Verification of the Positive Definiteness of the Inertial Matrix of Manipulators Using Base Inertial Parameters
Authors: Yoshida Koji , Khalil Wisama
Published: December 2004

The computation of the inertial matrix of dynamic model for manipulator using some sets of base-parameter values may be not positive definite for some configurations. Such sets of base-parameter values are physically impossible. The result of the study on physical impossibility of the set of base-parameter values could be used to judge if a set of base-parameter values, which are obtained through parameter identification or other methods, is physically impossible or not and to modify the set of base-parameter values that was judged to be physically impossible. Hence, the result would directly contribute to model-based control of manipulators or motion simulation for manipulators. In this paper, a sufficient condition for the inertial matrix to be positive definite for each configuration of the manipulator is given by use of physical inertial parameters of the links composing the manipulator. By use of this condition and a set of “virtual parameters,” a scheme is given to judge if a set of base-parameter values determine the inertial matrix to be always positive definite or not.
Discrete-Time Lyapunov Design for Neuroadaptive Control of Elastic-Joint Robots
Authors: Macnab C. J. B. , D’Eleuterio G. M. T.
Published: December 2004

A neural-network controller operating in discrete time is shown to result in stable trajectory tracking for rigid and elastic-joint robots. The technique assumes continuous-time state feedback. The proof of stability uses discrete-time Lyapunov functions. For the elastic-joint case, a discrete-time version of the adaptive backstepping technique is used. The result is that the neural network can be run at a very slow control rate, suitable for online calculations. The neural network used is referred to as the CMAC-RBF Associative Memory (CRAM), a modification of Albus’s Cerebellar Model Arithmetic Computer (CMAC) algorithm using radial basis functions (RBFs). Simulation results are provided for a two-link planar elastic-joint robot and show that performance can be improved by using a larger network at a slower control rate.
Reconstructing the Shape of a Deformable Membrane from Image Data
Authors: Ferrier Nicola J. , Brockett Roger W.
Published: December 2004

In this paper, we study the problem of determining a mathematical description of the surface defined by the shape of a membrane based on an image of it and present an algorithm for reconstructing the surface when the membrane is deformed by unknown external elements. The given data are the projection on an image plane of markings on the surface of the membrane, the undeformed configuration of the membrane, and a model for the membrane mechanics. The method of re construction is based on the principle that the shape assumed by the membrane will minimize the elastic energy stored in the membrane subject to the constraints implied by the measurements. Energy minimization leads to a set of nonlinear partial differential equations. An approximate solution is found using linearization. The initial motivation, and our first application of these ideas, comes from tactile sensing. Experimental results affirm that this approach can be very effective in this context.
Efficient Linear Unboundedness Testing: Algorithm and Applications to Translational Assembly Planning
Authors: Schwarzer Fabian , Schweikard Achim , Joskowicz Leo
Published: December 2004

We address the problem of efficiently testing for linear unboundedness and its applications to translational assembly planning. We describe a new algorithm that performs the test by solving a single homogeneous system of equations followed by a single linear feasibility test. We show that testing for unboundedness is computationally at least as hard as these two subproblems. The new algorithm is the fastest known algorithm and is practical. We then present a framework for general translational assembly planning based on linear constraints. We show the relation of m-handed assembly planning to unboundedness testing and present a polynomial-time algorithm for m-handed assembly of polygonal part assemblies with no initially separated pairs of parts. For the general translational assembly–planning problem, we present a new algorithm that uses unboundedness testing and a cell reduction technique to significantly increase the search efficiency. Experimental results of our implementation on a variety of planar and spatial assemblies demonstrate the practicality of the algorithms.
Conservative Congruence Transformation for Joint and Cartesian Stiffness Matrices of Robotic Hands and Fingers
Authors: Chen Shih-Feng , Kao Imin
Published: December 2004

In this paper, we develop the theoretical work on the properties and mapping of stiffness matrices between joint and Cartesian spaces of robotic hands and fingers, and propose the conservative congruence transformation (CCT). In this paper, we show that the conventional formulation between the joint and Cartesian spaces, K θ = J TθK pJ θ, first derived by Salisbury in 1980, is only valid at the unloaded equilibrium configuration. Once the grasping configuration is deviated from its unloaded configuration (for example, by the application of an external force), the conservative congruence transformation should be used. Theoretical development and numerical simulation are presented. The conservative congruence transformation accounts for the change in geometry via the differential Jacobian (Hessian matrix) of the robot manipulators when an external force is applied. The effect is captured in an effective stiffness matrix, K g, of the conservative congruence transformation. The results of this paper also indicate that the omission of the changes in Jacobian in the presence of external force would result in discrepancy of the work and lead to contradiction to the fundamental conservative properties of stiffness matrices. Through conservative congruence transformation, conservative and consistent physical properties of stiffness matrices can be preserved during mapping regardless of the usage of coordinate frames and the existence of external force.
Multiple Center of Mass Space Images of Single Objects and Their Impact on Path Planning
Authors: Doggett William R. , Messner William C. , Juang Jer-Nan
Published: December 2004

The center of mass space is a convenient space for planning motions that minimize reaction forces at the manipulator’s base or optimize the stability of a mechanism. A unique problem associated with path planning in the center of mass space is the potential existence of multiple center of mass images for a single Cartesian obstacle, since a single center of mass location can correspond to multiple manipulator joint configurations. The existence of multiple images results in a need to either maintain multiple center of mass obstacle maps or to update obstacle locations when the manipulator passes through a singularity, such as when it moves from an elbow-up to an elbow-down configuration. To illustrate the concepts presented in this paper, a path is planned for an example task requiring motion through multiple center of mass space maps. The object of the path-planning algorithm is to locate the path with a bang-bang acceleration profile that minimizes the manipulator’s base reactions in the presence of a single Cartesian obstacle. To simplify the presentation, only nonredundant manipulators are considered and joint nonlinearities are neglected.
A Catastrophe Theory Model of Planar Orientation
Authors: Wright Mark W. , Deacon Graham E.
Published: December 2004

The manipulation of planar objects using linear fences is of interest in robotics and parts feeding applications. The global behavior of such systems can be characterized graphically using Brost's push stability diagram (PSD). Previously, we have shown specifically under what conditions this representation undergoes qualitative, topological transitions corresponding to globally distinct behavioral regimes. In this paper, we show that these insights form a united Whole when viewed from the perspective of catastrophe theory. The key result is that a planar object being pushed by a fence under the assumption of Coulomb friction is functionally equivalent to a gravitational catastrophe mnachine. Qualitative changes in global behavior are thus explained as catastrophes as singularities are encountered on a discriminant surface due to smooth changes in parameters. Catastrophe theory thus forms part of a computational theory of planar orientation, the aim of which is to understand such systems and make predictions about their behavior.
A Trotting Horse Model
Authors: Herr Hugh M. , McMahon Thomas A.
Published: December 2004

A new control strategy is used to stabilize numerical simulations of a horse model in the trotting quadrupedal gait. Several well-established experimental findings are predicted by the model, including how stride frequency and stride length change with forward running speed. Mass is distributed throughout the model's legs, trunk, and head in a realistic manner. Leg and trunk flexion is modeled using four flexible legs, a back joint, and a neck joint. In the control model, pitch stabilization is achieved without directly controlling body pitch, but rather by controlling both the aerial time and the foot speed of each stance leg. The legs behave as ideal springs while in contact with the ground, enabling the model to rebound from the ground with each trotting step. Numerical experiments are conducted to test the model's capacity to overcome a change in ground impedance. Model stability is maximized and the metabolic cost of trotting is minimized within a narrow range of leg stiffness where trotting horses of similar body size have been observed to operate. This work suggests that a horselike robot will exhibit behavior that is mechanically similar to that of a trotting horse if it operates in a narrow range of leg stiffness and employs simple control strategies where postural stabilization is an emergent property of the system.
Fully Decentralized Estimation and Control for a Modular Wheeled Mobile Robot
Authors: Mutambara Arthur G. O. , Durrant-Whyte Hugh F.
Published: December 2004

In this paper, the problem of fully decentralized data fusion and control for a modular wheeled mobile robot (WMR) is addressed. This is a vehicle system with nonlinear kinematics, distributed multiple sensors, and nonlinear sensor models. The problem is solved by applying fully decentralized estimation and control algorithms based on the extended information filter. This is achieved by deriving a modular, decentralized kinematic model by using plane motion kinematics to obtain the forward and inverse kinematics for a generalized simple wheeled vehicle. This model is then used in the decentralized estimation and control algorithms. WMR estimation and control is this obtained locally using reduced order models with reduced communication requirements, in a scalable network of control nodes. If communication of information between nodes is carried out after every measurement (full rate communication), the estimates and control signals obtained at each node are equivalent to those obtained by a corresponding centralized system. Transputer architecture is used as the basis for hardware and software design as it supports the extensive communication and concurrency requirements that characterize modular and decentralized systems. The advantages of a modular WMR vehicle include scalability, application flexibility low prototyping costs, and high reliability.
Safe Task Planning Integrating Uncertainties and Local Maps Federations
Authors: Lambert Alain , Le Fort-Piat Nadine
Published: December 2004

This paper deals with the generation of safe tasks for displacement missions of a nonholonomic mobile robot in a mapped indoor environment. The goal of this study is to plan safe actions (path-following) as well as observations (we call it local maps federation [LMF]), leading the robot to configurations where pertinent features can be sensed, thus attaining best localization relative to its environment. A path-planning method dealing with uncertainties is proposed, where both uncertainties in localization and in control of a nonholonomic mobile robot are managed. Maps uncertainties are handled using the local map concept, which is introduced as a set of the best landmarks used for planning and executing robust motion movements. The safeness of the proposed method is due to the mixing between the planning phase and the navigation phase.
Objective and Frame-Invariant Kinematic Metric Functions for Rigid Bodies
Authors: Lin Qiao , Burdick Joel W.
Published: December 2004

Kinematic metric functions, which allow us to make metric measurements such as “distance,” “length,” and “angle,” are often needed in robotics. However, some commonly used metric functions are not well-defined because of their dependence on choice of reference frame. This paper presents formal and practical conditions for kinematic metric functions to be well-defined. To properly analyze this issue, we introduce an intrinsic formulation of the configuration space of a rigid body that does not depend on frames. Based on this intrinsic definition, the principle of objectivity, or observer indifference, is introduced to derive a formal condition for well-definedness of kinematic metric functions. The principle of objectivity is further used to gain physical insight into left, right, and bi-invariances on the Lie group SE(3). The abstract notion of objectivity is then related to the more practically useful notion of frame invariance, which is shown to be necessary and sufficient for objectivity. Thus, frame invariance can be used as a practical condition for determining objective functions, and we give an explicit formula to determine frame invariance of a given metric function. Finally, by use of examples, we present several frame-invariant norms of rigid body velocities and wrenches. These examples demonstrate that norms with interesting physical interpretations need not be derived from inner products of velocities or wrenches.
Tactile Sensing: New Directions, New Challenges
Authors: Lee Mark H.
Published: December 2004

Over the past three decades, tactile sensing has developed into a sophisticated technology. There has been a longstanding and widely held expectation that tactile sensors would have a major impact on industrial robotics and automation. However, this promise has not been realized, and few, if any, tactile sensors can be found in factory-based applications. Has this technology failed to deliver its expected benefits to robotics applications, or have other factors influenced the development of the field? In this paper, I report on the state of the art and show that tactile sensing has undergone a major change of direction. I revisit the original predictions and expectations, examine the implications of recent reviews, and show how the field has altered course. From current activities and recent trends, I determine the nature of new application areas and pressing developments that hold much promise for the future. There is evidence that tactile sensing will soon play a major role in unstructured environments, particularly in areas such as medicine and surgery, health-care and service robotics, and automated natural product handling.
Lorentz Magnetic Levitation for Haptic Interaction: Device Design, Performance, and Integration with Physical Simulations
Authors: Berkelman Peter J. , Hollis Ralph L.
Published: December 2004

A new Lorentz force magnetic levitation haptic interface device has been developed and integrated with real-time 3-D rigid-body simulations for detailed, responsive interaction with dynamic virtual environments. An ideal haptic interface device would enable remote or simulated objects to be sensed and manipulated in 6 degrees of freedom (DoF) in the same manner as real physical objects, with the same micrometer level of detail and kHz bandwidth response that the user can sense. To approach this level of performance requires stiff lightweight moving parts, responsive actuators, high-resolution sensors, a fast control system, and a real-time simulation closely integrated with the device. Lorentz levitation is well suited to high-performance, tool-based haptic interaction because noncontact actuation and sensing provide motion and force feedback in 6 DoF with the simple dynamics of a single moving part at high control bandwidths and sensitivity. New actuation and sensing subsystem designs greatly increase the user range of motion over previous maglev devices. The motion range of the new device is ± 12.5 mm in translation and ± 7.5 deg in rotation to accommodate haptic fingertip motion tasks. The device has a measured closed-loop position bandwidth of more than 100 Hz in each DoF, a maximum stiffness of 25.0 N/mm, and a position resolution of 5-10 μm. Virtual coupling and intermediate representation methods were implemented to combine the simulation and the device controller and maximize the realism of haptic user interaction when computational resources are limited. In our system, the device controller must cycle several times faster than the simulation to generate stiff constraints during stable levitation. With virtual coupling, the updated position and orientation data from the interface device and the simulated tool act as error and velocity feedback control setpoints for each other. With the contact point intermediate representation method, a list of current tool contact points and directions is generated at each update of the simulation so that the device controller can evalute contact constrains locally and change impedance to respond to user motions at the fast control rate rather than the slower simulation rate. The contact point intermediate representation provides a crisper, more responsive feeling than virtual coupling during interaction but is not as easily stabilized. Experimental data from the virtual coupling and a modified contact point intermediate representation are presented.
Ray-Based Haptic Rendering: Force and Torque Interactions between a Line Probe and 3D Objects in Virtual Environments
Authors: Ho Chih-Hao , Basdogan Cagatay , Srinivasan Mandayam A.
Published: December 2004

Virtual environments (VEs) that enable the user to touch, feel, and manipulate virtual objects through haptic interactions are expected to have applications in many areas such as medicine, CAD/CAM, entertainment, fine arts, and education. The current state of technology allows the human operator to interact with virtual objects through the probe (such as a thimble or a stylus) of a force-reflecting haptic interface. Most of the current haptic interaction algorithms model the probe as a single point and allow the user to feel the forces that arise from point interactions with virtual objects. In this paper, we propose a ray-based haptic-rendering algorithm that enables the user to touch and feel convex polyhedral objects with a line segment model of the probe. The ray-based haptic-rendering algorithm computes both forces and torques due to collisions of the tip and/or side of the probe with multiple virtual objects, as required in simulating many tool-handling applications. Since the real-time simulation of haptic interactions between a 3D tool and objects is computationally quite expensive, the ray-based rendering can be considered as an intermediate step toward achieving this goal by simplifying the computational model of the tool. To compare the ray- and point-based haptic interaction techniques in the haptic perception of 3D objects, we conducted perceptual experiments in which the participants were asked to identify the shape of four different 3D primitives (sphere, cone, cylinder, and cube) that were displayed in random order using both point-and ray-based techniques. The results of the study show that on average, 3D objects are recognized faster with ray-based rendering than with point-based rendering.
Experiments in Fingertip Perception of Surface Discontinuities
Authors: Venema Steven C. , Hannaford Blake
Published: December 2004

In this paper, we present the results of experiments that explore the ability of the human fingertip to detect haptically simulated first-order and second-order surface discontinuities. A single finger, planar motion fingertip haptic display (FHD) developed at the University of Washington was used by multiple test operators to kinesthetically trace haptically simulated surfaces under a variety of treatment conditions. Experiment variables included the magnitude and type of discontinuity, as well as the stiffness and damping terms used in the haptic simulation algorithm. Test operators were asked to haptically locate a discontinuity on a simulated surface for each treatment condition with the location accuracy being used as the experiment performance metric. The results reveal how the surface discontinuity detection ability is degraded by control gains that are either too low or too high, indicating that a given haptic simulation system may have an optimum set of control gains that will yield the best performance for this type of task.
Reactive Robotics I: Reactive Grasping with a Modified Gripper and Multifingered Hands
Authors: Teichmann Marek , Mishra Bud
Published: December 2004

We study the problem of grasping an unknown object with constant cross section using various “reactive” robot hands. In the simplest example, we equip a standard parallel-jaw gripper with several light-beam sensors (close to each jaw) and implement a reactive algorithm for grasping polygonal objects with this architecture. Extending these ideas further, we also devise two-and three-fingered reactive hands for objects with smooth boundary and equip these with distance and angle sensors that are located at the finger tips. The sensors used are simple and provide only limited and immediate information, but they allow us to reactively find a good grasp on an object of unknown geometry and dynamics. When grasped, the forces applied will be normal to the object boundary. Furthermore, in all cases, the object is not disturbed as the grasping points are being sought.
Feature-Based Mapping in Real, Large Scale Environments Using an Ultrasonic Array
Authors: Chong Kok Seng , Kleeman Lindsay
Published: December 2004

This paper presents a strategy for achieving practical mapping navigation using a wheeled mobile robot equipped with an advanced sonar sensor The original mapping navigation experiment, carried out with the same robot configuration, built a feature map consisting of common-place indoor landmarks crucial for localization; namely, planes, corners, and edges. The map exhaustively maintained covariance matrices among all features, and thus presented a time and memory impediment to practical navigation in large environments. The new local mapping strategy proposed here breaks down a large environment into a topology of local regions, only maintaining the covariance among features in the same local region, and the covariance among local maps. This notion of two-hierarchy representation drastically improves the memory and processing-time requirements of the original global approach, while preserving the statistical details, in the authors' opinions, necessary for an accurate map and prolonged navigation. The new local mapping scheme also extends the endeavor toward reducing error accumulation made in the global mapping strategy by eliminating errors accumulated between visits to the same part of the environment. This is achieved with a map-matching strategy developed exclusively for the advanced sonar sensor that is employed. The local mapping strategy has been tested in two large, real-life indoor environments, and successful results are reported here.
Mobile-Robot Map Building from an Advanced Sonar Array and Accurate Odometry
Authors: Chong Kok Seng , Kleeman Lindsay
Published: December 2004

This paper describes a mobile robot equipped with a sonar sensor array in a guided, feature-based map-building task in an indoor environment. The landmarks common to indoor environments areplanes, corners, and edges, and these are located and classified with the sonar sensor array The map-building process makes use of accurate odometry information that is derivedfiom apair ofknife-edged unloaded encoder wheels. Discrete sonar observations are incrementally merged into partial planes to produce a realistic representation of the environment that is amenable to sonar localization. Collinearity constraints among featurs ar exploited to enhance both the map-featwe estimation and robot localization. The map update employs an iterated extended Kalmanfilter in the first implementation and subsequently a comparison is made with the Julier-Uhlmann-Durrant-Whyte Kalman filter which improves the accuracy of covariance propagation when nonlinear equations are involved. The map accounts for correlation among features and robot positions. Partial planes am also used to eliminate phantom targets caused by specular reflection of the sonar. Unclassifiable sonar targets are integrated into the map for the purpose of obstacle avoidance. The paper presents simulated and experimental data.
Scaling the Dynamic Approach to Path Planning and Control: Competition among Behavioral Constraints
Authors: Large Edward W. , Christensen Henrik I. , Bajcsy Ruzena
Published: December 2004

The dynamic-systems approach to robotpathplanningdefinesa dynamics ofrbotbehavior in which task constraints contribute independently to a nonlinear vector field that governs robot actions. We address problems that arise in scaling this approach to handle complex behavioral requirements. We propose a dynamics that operates in the space of task constraints, determining the relative contribution of each constraint to the behavioral dynamics. Competition among task constraints is able to deal with problems that arise when combining constraint contributions, making it possible to specify tasks that are mome complex than simple navigation. To demonstrate the utility of this approach, we design a system of two agents to perform a cooperative navigation task We show how competition among constraints enables agents to make decisions regarding which behavior to execute in a given situation, resulting in the execution of sequences of behaviors that satisfy task requirements. We discuss the scalability of the competitive-dynamics approach to the design of more complex autonomous systems.
Practical Sliced Configuration Spaces for Curved Planar Pairs
Authors: Sacks Elisha
Published: December 2004

In this article, Ipresenta practical configuration-space computation algorithm for pairs of cwvedplanarparts, based on the general algorithm developed by Bajaj and me. The general algorithm advances the theoretical understanding of configuration-space computation, but is too slow andfragilefor some applications. The new algorithm solves these problems by restricting the analysis to parts bounded by line segments and circular arms, whereas the general algorithm handles rationalparametric curves. The trade-off is worthwhile, because the restricted class handles most robotics and mechanical engineering applications. The algorithm reduces run time by a factor of 60 on nine representative engineering pairs, and by a factor of 9 on two human-knee pairs. It also handles common specialpairs by specialized methods. A survey of 2,500 mechanisms shows that these methods cover 90%/O ofpairs and yield an additionalfactor of 10 reduction in average run time. The theme of this article is that application requirements, as well as intrinsic theoretical interest, should drive configuration-space research.
Dynamic Nonprehensile Manipulation: Controllability, Planning, and Experiments
Authors: Lynch Kevin M. , Mason Matthew T.
Published: December 2004

We are interested in using low-degree-of-freedom robots to perform complex tasks by nonprehensile manipulation (manipulation without aformorforce-closure grasp). By notgrasping, the robot can usegravitational, centrifugal, and Coriolisforces as virtual motors to control more degrees of freedom of the part. The part s extra motionfreedoms are exhibited as rolling, slipping, and free flight.

This paper describes controllability, motion planning, and implementation ofplanar dynamic nonprehensile manipukltion. We show that almost any planar object is controllable by point contact, and the controlling robot requires only twvo degrees of freedom (a point translating in the plane). We then focus on a one-joint manipulator (with a two-dimensional state space), and show that even this simplest of robots, by using slipping and rolling, can control a planar object to a fulldimensional subset of its six-dimensional statespace. We have developed a one-jointrobotto perform a variety of dynamic tasks, including snatching an object ftom a table, rolling an object on the surface of the arm, and throwing and catching. Nonlinear optimization is used to plan robot trajectories that achieve the desired object motion via coupling forces though the nonprehensile contact.
Nonlinear Dynamics and Chaotic Motions in Feedback-Controlled Two-and Three-Degree-of-Freedom Robots
Authors: Ravishankar A. S. , Ghosal Ashitava
Published: December 2004

The dynamics of a feedback-controlled rigid robot is most commonly described by a set of nonlinear ordinary differential equations. In this paper we analyze these equations, representing the feedback-controlled motion of twoand three-degrees-of-freedom rigid robots with rnvolute (R) and prismatic (P) joints in the absence of compliance, friction, and potential energy for the possibility of chaotic motions.

We first study the unforced or inertial motions of the robots, and show that when the Gaussian or Riemannian curvature of the configuration space of a robot is negative, the robot equations can exhibit chaos. If the curvature is zero or positive, then the robot equations cannot exhibit chaos. We show that among the two-degrees-of-freedom robots, the PP and the PR robot have zer Gaussian curvature while the RP and RR rohots have negative Gaussian curvatures. For the three-degrees-offireedom robots, we analyze the two well-known RRP and RRR configurations of the Stanford arm and the PUMA manipulator, respectively, and derive the conditions for negative curvature and possible chaotic motions. The criteria of negative curvature cannot be usedfor the forced or feedback-controlled motions. For the foired motion, we resort to the well-known numerical techniques and compute chaos maps, Poincard maps, and bifurcation diagrams. Numerical results are presentedfor the two-degreesf-ffreedom RP and RR robots, and we show that these robot equations can exhibit chaos for low controller gains and for large underestimated models. From the bifurcation diagrams, the mute to chaos appears to he through period doubling.
On Closed Form Expressions for the Singular-Value Decomposition of an Orientational Jacobian and Its Application to a Motion Simulator
Authors: Roberts Rodney G. , Repperger Daniel W.
Published: December 2004

This article presents some results on the closed-form, singular-value decomposition of the orientational Jacobian for threeand four-degreeof-freedom wristlike mechanisms. These results are used to study the kinematics of a centrifuge simulator and to determine the centrifuge s limitations in achieving maximum angular velocities. Also, the issue of fault tolerance for a redundant wrist is addressed.
Analytical Expression for the Inverted Inertia Matrix of Serial Robots
Authors: Saha Subir Kumar
Published: December 2004

This paper presents the analytical derivation of the inertia matrix and its inverse for an open-loop, serial-chain mbot. The derivation allows one to write a recursiveforward-dynamics algorithmforsimulation purposes whose computational complexity is of order a, i.e., O(n) n being the degrees offreedom of the robot under study The proposed methodology is based on the Gaussian elimination of the inertia matrix, in contrast to, say, Kalmanftltering; which is proposed elsewhere. The derivation is illustrated with a three-degrees-of-freedom planar robot.
Control of Sensory Perception in a Mobile Navigation Problem
Authors: Hovland G. E. , McCarragher B. J.
Published: December 2004

The problem of controlling sensory input and perception for use in mobile navigation is addressed in this paper. The proposed solution offers several advantages compared with existing methods in the literature. First, the proposed solution is based on a stochastic dynamic-programming algorithm that guarantees cost efficiency of the real-time sensory-perception controller by solving a constrained optimization problem. Second, a new and unique discrete-event model of mobile navigation is presented. The model is task independent, and can be used in a wide range of applications. Third, the discrete events become a natural common representational format for the sensors, which further extends the applicability of the proposed solution. Fourth, the sensing aspect of discrete-event systems has often been neglected in the literature. In this paper, we present a unique approach to on-line discrete-event identification.
Encoding and Decoding of Static Information in Tactile Sensing Systems
Authors: Kárason S. P. , Srinivasan M. A. , Annaswamy A. M.
Published: December 2004

Human and robot tactile sensing can be accomplished by arrays of mechanosensors embedded in a deformable medium. When an object comes in contact with the surface of the medium, information about the shape of the medium's surface and the force distribution within the region of contact on the surface is available in the stress/strain states at the sensor locations within the medium. The mechanosensors transduce these signals, and the problem for the central processor is to reliably and efficiently infer the contact state and the object properties on the surface from the sensor signals. In this paper, a frequency-domain approach is used to solve the problem of encoding and decoding mechanosensory information. A Solution to the encoding problem is given with the medium modeled as a general three-dimensional infinite half-space composed of a linear elastic material and subjected to three-dimensional loads. It is shown that considerations of symmetry and bandwidth of sensor response uniquely determine the optimal stress/strain components the sensors need to transduce. It is further shown how the decoding leads to an ill-posed problem, and how that problem can be effeciently solved in the frequency domain using a regularized inverse such as the multivariate Wiener inverse. The results are the applied to the encoding and decoding of contact with a shaped object. It is shown that the solution can also be used in pseudodynamic problems, such as the estimation of the onset of slip.
An Arbitrarily Distributed Tactile-Sensor Array Based on a Piezoelectric Resonator
Authors: Li Ping , Wen Yumei
Published: December 2004

This paper introduces a new principle and real structure of a nonscaning, fast-response, arbitrarily distributed tactile-sensor array using a piezoelectiric resonator. The piezoelectric sensor has high stability, and the quasi-digital output can be measured easily and precisely. The sensory position can also be measured quickly and precisely. In addition, the tactile sensor array of soft piezoelectric film is adaptive to the sensitive skin of robot.
Properties of the Grasp Stiffness Matrix and Conservative Control Strategies
Authors: Kao Inmin , Ngo Chi
Published: December 2004

In this paper, we present fundamental properties of stiffness matrices as applied in analysis of grasping and dextrous manipulation in configuration spaces and linear Euclidean R3×3 space without rotational components. A conservative-stiffness matrix in such spaces needs to satisfy both symmetric and exact differential criteria. Two types of stiffness matrices are discussed: constant and configuration-dependent matrices. The symmetric part of a constant-stiffness matrix can be derived from a conservative quadratic potential function in the Hermitian form; while the skew-symmetric part is a function of the nonconservative curl vector field of the grasp. A configuration-dependent stiffness matrix needs to be symmetric and must simultaneously satisfy the exact differential condition to be conservative. The theory is most relevant to the Cartesian stiffness control, where the stiffness of the end effector is usually constant, such as that in RCC wrists. Conservative control strategies are proposed for a configuration-dependent stiffness matrix. One of the most important results of this paper is the nonconservative congruence mapping of stiffness between the joint and Cartesian spaces. In general, the congruence transformation (or its inverse transformation), Kθ = JTθKpJθ, is a nonconservative mapping over finite paths for a configuration-dependent Jacobian. Thus, to obtain a conservative system with respect to the Cartesian space, one has to either find the corresponding Kθ at every configuration due to the constant and symmetric Cartesian stiffness matrix, or determine the symmetric yet configuration-varying Kθ which makes the resulting configuration-dependent Kp conservative. In addition, the stiffness matrix also must be positive definite to maintain stability.