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Robotics and Automation, IEEE Transactions on

Issue 5 • Date Oct 1999

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Displaying Results 1 - 17 of 17
  • Generalized recognition of single-ended contact formations

    Page(s): 829 - 836
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    Contact formations have proven useful for programming robots by demonstration for operations involving contact. These techniques require real time recognition of contact formations. Single ended contact formation (SECF) classifiers using only the force/torque measured at the wrist of the robot have been shown to be quite effective for this purpose. To function properly, however, previous SECF classifiers have required a sizable training set and a constant pose between the force/torque sensor and the manipulated object. Thus, if an object is re-grasped and the pose changes, one expects to have to repeat the creation of the training set. We discuss the impact of sensor-object pose changes have on two successful classifiers. Experimental data shows that they perform poorly when sensor-object pose changes. We discuss a method to regain the performance of both classifiers while minimizing the retraining necessary View full abstract»

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  • Distributed memoryless point convergence algorithm for mobile robots with limited visibility

    Page(s): 818 - 828
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    We present a distributed algorithm for converging autonomous mobile robots with limited visibility toward a single point. Each robot is an omnidirectional mobile processor that repeatedly: 1) observes the relative positions of those robots that are visible; 2) computes its new position based on the observation using the given algorithm; 3) moves to that position. The robots' visibility is limited so that two robots can see each other if and only if they are within distance V of each other and there are no other robots between them. Our algorithm is memoryless in the sense that the next position of a robot is determined entirely from the positions of the robots that it can see at that moment. The correctness of the algorithm is proved formally under an abstract model of the robot system in which: 1) each robot is represented by a point that does not obstruct the view of other robots; 2) the robots' motion is instantaneous; 3) there are no sensor and control error; 4) the issue of collision is ignored. The results of computer simulation under a more realistic model give convincing indication that the algorithm, if implemented on physical robots, will be robust against sensor and control error View full abstract»

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  • Load adaptive control of single-link flexible arms based on a new modeling technique

    Page(s): 793 - 804
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    A new method for controlling single-link flexible manipulators is proposed. The objective is to control the tip position of a flexible manipulator in the presence of changes in its payload. Particularly, a new adaptive control system has been designed. The proposed control system requires calculating only one parameter, the tip load, instead of all the transfer functions as in conventional adaptive control methods. The tip load identification algorithm is based on the equivalence existing between a manipulator with payload and a manipulator submitted to the action of external forces. Moreover, this equivalence provides a new technique for modeling these systems which simplifies the methods usually applied. This results in a simple control law that needs minimal computing effort and, thus, can be used for real-time control of flexible arms View full abstract»

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  • Part pose statistics: estimators and experiments

    Page(s): 849 - 857
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    Many of the most fundamental examples in probability involve the pose statistics of coins and dice as they are dropped on a flat surface. For these parts, the probability assigned to each stable face is justified based on part symmetry, although most gamblers are familiar with the possibility of loaded dice. In industrial part feeding, parts also arrive in random orientations. We consider the following problem: given part geometry and parameters such as center of mass, estimate the probability of encountering each stable pose of the part. We describe three estimators for solving this problem for polyhedral parts with known center of mass. The first estimator uses a quasistatic motion model that is computed in time O(n log n) for a part with n vertices. The second estimator has the same time complexity but takes into account a measure of dynamic stability based on perturbation. The third estimator uses repeated Monte Carlo experiments with a mechanics simulation package. To evaluate these estimators, we used a robot and computer vision system to record the pose statistics based on 3595 physical drop experiments with four different parts. We compare this data to the results from each estimator. We believe this is the first paper to systematically compare alternative estimators and to correlate their performance with statistically significant experiments on industrial parts View full abstract»

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  • The SPmap: a probabilistic framework for simultaneous localization and map building

    Page(s): 948 - 952
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    This article describes a rigorous and complete framework for the simultaneous localization and map building problem for mobile robots: the symmetries and perturbation map (SPmap), which is based on a general probabilistic representation of uncertain geometric information. We present a complete experiment with a LabMateTM mobile robot navigating in a human-made indoor environment and equipped with a rotating 2D laser rangefinder. Experiments validate the appropriateness of our approach and provide a real measurement of the precision of the algorithms View full abstract»

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  • On the use of scaling matrices for task-specific robot design

    Page(s): 958 - 965
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    Good robot performance often relies upon the selection of design parameters that lead to a well conditioned Jacobian or impedance “design” matrix. In this paper, a new design matrix normalization technique is presented to handle the problem of nonhomogeneous physical units and to provide a means of specifying a performance based design goal. The technique pre- and post-multiplies a design matrix by scaling matrices corresponding to a range of joint and task space variables. The task-space scale factors are used to set the relative required strength or speed along any axes of end point motion while the joint-space scale factors are treated as free design parameters to improve isotropy through nonhomogeneous actuation. The effect of scaling on actual designs is illustrated by a number of design examples using a global search method previously developed by the authors View full abstract»

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  • On the equivalence of internal and interaction forces in multifingered grasping

    Page(s): 934 - 941
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    This paper deals with the problem of the equivalence of internal and interaction forces in multifingered grasping. The dimensions of these two force spaces are analyzed. It is shown that the internal force space can be more generally expressed as the direct sum of the interaction and parallel force spaces. Under certain conditions, the parallel force space disappears and the internal and interaction force spaces become coincident. In this sense, the internal force can be equivalently characterized by the interaction force or pairs of equal and opposite collinear forces. The necessary and sufficient conditions for this equivalent characterization, which depends upon the number of contacts and the distribution of their locations, are derived. The algebraic structure of the parallel force spaces is given. Some illustrative examples are also presented View full abstract»

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  • Planning quasi-static fingertip manipulations for reconfiguring objects

    Page(s): 837 - 848
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    We address the global motion planning aspects of dexterous manipulation by a multifingered robotic hand. The specific task we address is: starting from a given initial grasp of a three-dimensional (3-D) object O, find feasible quasistatic trajectories (rolling/sliding motions and forces) for the fingertips to move O to a desired final configuration. We call this the reconfiguration problem. Our planner is based on a two-level algorithm combining a graph search on the configuration space of the object and a local planner that solves for instantaneous quasistatic motions of the entire manipulation system. The planner is used for simulating several complex reconfiguration tasks for smooth objects demonstrating the promise of our approach View full abstract»

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  • Iterative multistep explicit camera calibration

    Page(s): 897 - 917
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1084 KB)  

    Perspective camera calibration has been a research subject for a large group of researchers. However, only a small number of those methods base their approaches on the use of monoplane calibration points. We developed one of those methodologies using monoplane calibration points to perform an explicit three-dimensional (3-D) camera calibration. This methodology is based on an iterative approach. To avoid the singularities obtained with the calibration equations when monoplane calibration points are used, this method computes the calibration parameters in a multistep procedure and requires a first-guess solution for the intrinsic parameters. These intrinsic parameters are updated and their accuracy increased during the iterative procedure. All computations required are linear and in addition to the extrinsic parameters the proposed method also computes the first coefficient of the radial distortion (k1) and the skew angle. A first-guess value for the focal length of the lens is required but its value is iteratively updated using the Gauss lens model. This methodology also includes the uncertainty horizontal image scale factor (Sx) on the set of calibration parameters to be computed, which makes this approach independent of the accuracy of the horizontal scale factor. The proposed methodology has the advantage that it can be used with monoplane calibration data with no restrictions for the pose geometry of the camera. In this approach the pose estimation problem is treated separately, computing the pose orientation of the camera in a first step and using this information to compute the pose location. A model for the expected stability of the camera look angles from noisy image data and its stability analysis as a function of the pose geometry of the camera is presented. Several experimental and simulated analyzes were performed and are presented View full abstract»

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  • Lead time modeling and acceleration of product design and development

    Page(s): 882 - 896
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    New product development is an important business process and constitutes a major contributor to the business excellence of any manufacturing firm. Designing an optimized new product development process is an important problem in itself and is of significant practical and research interest. Lead time is an important performance metric for a product development organization. We develop lead time models for product development organizations that involve multiple, concurrent projects with contention for human/technical resources. The objective is to explore how the lead times call be reduced using efficient scheduling, input control, load balancing, and variability reduction. The models are based on single class and multiclass queueing networks and capture important facets of a product development organization. Within the new product development process, we focus attention on the product design process. Two product design organizations, which we call Company ABC and Company XYZ, provide the real-world setting for our model-based lead time reduction. First, we present a coarse, conceptual queueing network model of Company ABC and show how rapid performance analysis can be used to explore opportunities for accelerating the design process. In particular, we show how effective input control, process control, load balancing, and cross-functional work can cut the lead times. Next, we present multiclass queueing network models for both the companies ABC and XYZ. The re-entrant line models show up certain scheduling issues pertaining to internal flows in the product design network. Using a class of fluctuation smoothing scheduling policies, we demonstrate how lead times can be reduced appreciably, without committing additional resources. The models presented are sufficiently generic and conceptual, and will be of much value in project planning and management in product design organizations and also more generally in product development organizations View full abstract»

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  • Design-specific approach to design for assembly (DFA) for complex mechanical assemblies

    Page(s): 869 - 881
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    Uses assembly sequence analysis (ASA) to explore design for assembly (DFA), subassembly partitioning, and assembly sequence choice for two complex assemblies. Complex assemblies have very high parts-counts, a final assembly organized as an assembly of subassemblies, and offer limited redesign options. ASA addresses combinatorial aspects of complex assemblies that conventional DFA ignores: choice and partitioning of subassemblies, and assembly sequence choice. The paper describes criterion-based searches for favorable subassembly partitioning and assembly sequences that use genetic algorithm techniques to spread assembly move difficulty across entire final assembly sequences while satisfying all logical constraints imposed on the assembly sequence by part geometry. The measure of assembly move difficulty, a count of kinematic degrees of freedom secured during each final assembly step, is measured on an absolute scale. We find that ASA can pinpoint candidate DFA-related redesigns and can suggest assembly issues to designers. Logical assembly issues dominate quantitatively-characterized issues when selecting assembly sequence or subassembly partitioning. After logical issues are addressed, the sequence choice criterion defined here often duplicates choices made by experienced analysts. Finally, the sequence choice criterion favors in-line over branched final assembly lines View full abstract»

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  • Minimal realization of a spatial stiffness matrix with simple springs connected in parallel

    Page(s): 953 - 958
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB)  

    This article presents a method for determining a minimal realization of an arbitrarily specified stiffness dominated spatial impedance through the use of a mechanism constructed of passive springs. This mechanism consists of simple springs connected in parallel where the term simple spring refers to a purely translational or purely rotational passive spring. Not every stiffness matrix K can be realized with a parallel connection of simple springs. The characterizing condition is that the upper right 3×3 submatrix of K has zero trace. Using this condition, the author shows how one can always synthesize any realizable spatial stiffness matrix with r parallel simple springs, where r is the rank of K. These results are also applicable to realizing a spatial damping matrix View full abstract»

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  • Distributed covering by ant-robots using evaporating traces

    Page(s): 918 - 933
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1024 KB)  

    We investigate the ability of a group of robots, that communicate by leaving traces, to perform the task of cleaning the floor of an un-mapped building, or any task that requires the traversal of an unknown region. More specifically, we consider robots which leave chemical odour traces that evaporate with time, and are able to evaluate the strength of smell at every point they reach, with some measurement error. Our abstract model is a decentralized multi-agent adaptive system with a shared memory, moving on a graph whose vertices are the floor-tiles. We describe three methods of covering a graph in a distributed fashion, using smell traces that gradually vanish with time, and show that they all result in eventual task completion, two of them in a time polynomial in the number of tiles. Our algorithms can complete the traversal of the graph even if some of the agents die or the graph changes during the execution, as long as the graph stays connected. Another advantage of our agent interaction processes is the ability of agents to use noisy information at the cost of longer cover time View full abstract»

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  • Identification of inertial and friction parameters for excavator arms

    Page(s): 966 - 971
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    A novel yet simple approach for experimental determination of the link (mass and inertia-related) parameters and friction coefficients is developed for a typical excavator arm. The parameters are needed for indirect measurement of the external forces, compensation for the link weights in the operator's hand in a force-feedback teleoperation setup, impedance control of the arm, simulation of the manipulator dynamics, and model-based fault detection. Treating the machine arm as an open kinematic chain, its dynamic equations are presented symbolically. The static torque equations are derived from these equations and the gravitational parameters are defined accordingly. A new method for decoupled estimation of the gravitational parameters from static experiments is presented. Furthermore, the arm dynamics are expressed in a form which is linear in the inertia and friction-related parameters. The results obtained show that the identified model predicts the joint torques, in both static and dynamic conditions, with a very good accuracy View full abstract»

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  • Experiments in aligning threaded parts using a robot hand

    Page(s): 858 - 868
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    Techniques for determining and correcting threaded part alignment using force and angular position data are developed to augment currently limited techniques for aligning threaded parts. These new techniques are based on backspinning a nut with respect to a bolt and measuring the force change that occurs when the bolt “falls” into the nut. Kinematic models that describe the relationship between threaded parts during backspinning are introduced and are used to show how angular alignment may be determined. The models indicate how to distinguish between the aligned and misaligned cases of a bolt and a nut connection by using axial force data only. In addition, by tracking the in-plane relative attitude of the bolt during spinning, data can be obtained on the direction of the angular misalignment which, in turn, is used to correct the misalignment. Results from experiments using a bolt held in a specialized fixture and a three fingered Stanford/JPL hand are presented View full abstract»

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  • Virtual truss model for characterization of internal forces for multiple finger grasps

    Page(s): 941 - 947
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    It is well known that any internal force for three finger grasps with frictional point contacts can usually be decomposed into three pushing or pulling force components along the three lines joining the contact points. This paper studies the question of how far this intuitive decomposition can go for general multiple finger grasps. We propose a virtual truss model for the grasped object for characterizing the internal force and show that this characterization is valid for general multiple finger grasps under a nondegeneracy condition. We also discuss some degenerate cases and give a method of extending the virtual truss model to cope with these special cases. Based on this characterization, we give an explicit formulation of the categorization by Ponce et al. (1993) of four finger grasps into concurrent, pencil, and regulus grasps. A procedure is also given for obtaining a nonredundant expression of all possible internal forces from this characterization View full abstract»

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  • Robust adaptive fuzzy-neural controllers for uncertain nonlinear systems

    Page(s): 805 - 817
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    A robust adaptive fuzzy-neural controller for a class of unknown nonlinear dynamic systems with external disturbances is proposed. The fuzzy-neural approximator is established to approximate an unknown nonlinear dynamic system in a linearized way. The fuzzy B-spline membership function (BMF) which possesses a fixed number of control points is developed for online tuning. The concept of tuning the adjustable vectors, which include membership functions and weighting factors, is described to derive the update laws of the robust adaptive fuzzy-neural controller. Furthermore, the effect of all the unmodeled dynamics, BMF modeling errors and external disturbances on the tracking error is attenuated by the error compensator which is also constructed by fuzzy-neural inference. We prove that the closed-loop system which is controlled by the robust adaptive fuzzy-neural controller is stable and the tracking error will converge to zero under mild assumptions. Several examples are simulated in order to confirm the effectiveness and applicability of the proposed methods View full abstract»

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Aims & Scope

This Transactions ceased production in 2004. The current retitled publications areIEEE Transactions on Automation Science and Engineering and IEEE Transactions on Robotics.

Full Aims & Scope