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Robotics and Automation, 1998. Proceedings. 1998 IEEE International Conference on

Date 20-20 May 1998

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  • Proceedings 1998 IEEE International Conference On Robotics And Automation

    Page(s): i - li
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  • Resource modelling and combination in modular robotics systems

    Page(s): 3167 - 3172 vol.4
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    Modular robotics systems (MRS) model robotics resources as distinct functional modules which are combined to perform tasks. MRS are flexible in both functionality and control, allowing a range of modules and control architectures to be used without modification of modules. This flexibility must be supported by a modelling strategy which allows specification of a module's functionality, and a well-defined mechanism for combining modules. This paper presents a sensor-oriented functional model of modular robotics systems. We describe our approach to modelling robotics resources, which uses semantic annotations to enhance the specification of functionality. A mechanism which successfully detects and resolves consequences of module combination is described, and results from our implementation of this mechanism presented. We outline the application of this work to the automatic configuration of varying control architectures without modification of modules or additional burden on the operator View full abstract»

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  • Development of a hand-to-hand robot based on agent network

    Page(s): 3516 - 3521 vol.4
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    This paper proposes the concept of “agent networks” to realize flexible and unified integration of multi-agent intelligent robot systems. As an example, we developed a hand-to-hand robot on the agent network. Its robust and flexible behaviour proved the effectiveness of the method View full abstract»

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  • Motion control of the NTUA robotic snake on a planar surface

    Page(s): 2977 - 2982 vol.4
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    We extend our previous work (1997, 1998) on steering a robotic snake and we now address the problems of (i) stabilization about an arbitrary configuration and (ii) tracking an arbitrary trajectory. For stabilization we apply three different algorithms for the kinematic model derived in the previous work. Comparisons of the three feedback stabilizing controls are made. Trajectory tracking is firstly addressed under the notion of flat systems. In a second approach we make use of a dynamic state feedback in order to achieve dynamic decoupling of our system View full abstract»

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  • Computation of kinetostatic performances of robot manipulators with polytopes

    Page(s): 3241 - 3246 vol.4
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    The kinetostatic analysis of manipulator performances at the end effector (EE) has traditionally been based on the computation of the so-called manipulability ellipsoids rather than on polytopes which are more accurate a representation. A reason why polytopes have received less attention is their being less tractable from a computational viewpoint. This paper presents an effective computation tool based on polytopes, with separation between translational and rotational analyses. This eliminates the ambiguity inherent in the conventional rototranslational formulation. Examples of application of this tool to the kinetostatic performance analysis of a redundant arm are finally provided, with numerical results View full abstract»

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  • Path planner for nonholonomic mobile robot with fast replanning procedure

    Page(s): 3588 - 3593 vol.4
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    This paper presents a new method of the path planning for robots with nonholonomic constraints in a partially known workspace. The method has been discussed for the car like robot with the three dimensional configuration space. The algorithm of the presented method is based on a A* graph searching with nodes placed in discretised configuration space. The graph generation process is driven by a heuristic cost which is found with the aid of a cost propagation procedure. This accelerates the searching without losing the optimality. The method presented is equipped with procedures of fast path replanning which is especially important for cases with partially known workspaces View full abstract»

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  • Rapid 3-D digitizing and tool path generation for complex shapes

    Page(s): 2789 - 2794 vol.4
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    A system for automatic tool path generation was developed at Sandia National Laboratories for finish machining operations. The system consists of a commercially available 5-axis milling machine controlled by Sandia developed software. This system was used to remove overspray on cast turbine blades. A laser-based, structured-light sensor, mounted on a tool holder, is used to collect 3D data points around the surface of the turbine blade. Using the digitized model of the blade, a tool path is generated which will drive a 0.375" CBN grinding pin around the tip of the blade. A fuzzified digital filter was developed to properly eliminate false sensor readings caused by burrs, holes and overspray. The digital filter was found to successfully generate the correct tool path for a blade with intentionally scanned holes and defects. The fuzzified filter improved the computation efficiency by a factor of 25. For application to general parts, an adaptive scanning algorithm was developed and presented with simulation and experimental results. A right pyramid and an ellipsoid were scanned successfully with the adaptive algorithm in simulation studies. In actual experiments, a nose cone and a turbine blade were successfully scanned. A complex shaped turbine blade was successfully scanned and finish machined using these algorithms View full abstract»

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  • Teleoperation system via computer network for dynamic environment

    Page(s): 3534 - 3539 vol.4
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    A teleoperation system in a dynamic environment with varying communication time delay is proposed, which consists of three subsystems; a bilateral teleoperation subsystem, a visual information subsystem, and an environment predictive display subsystem. The bilateral teleoperation subsystem is stabilized using the virtual time delay method. The visual information subsystem transfers the visual information in the remote site to the operator's site using the computer network. The environment predictive display subsystem estimates the behaviour of the environment and gives the predicted behaviour to the operator. An experimental system is developed and several experiments illustrate the effectiveness of the proposed system View full abstract»

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  • Transition stability of enveloped objects

    Page(s): 3040 - 3046 vol.4
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    This paper discusses the transition stability in sliding an object enveloped by a multi-fingered robot hand whose joints are under constant torque command. We provide a new concept on transition stability, where a transition is called stable if the object is guaranteed to reach the goal section without moving away from a virtual cylinder defined in hand working space. To evaluate the transition stability, we introduce the force-flow-diagram enabling us to confirm whether the object moves to the designated direction or not. By using the diagram, we discuss the transition stability in lifting up an object to the palm under gravitational force. Simulation results show that the transition phase for a column object with concave surface is stable, while that having convex surface tends to be unstable. We also show experimental results to confirm the basic behaviours during the transition phase View full abstract»

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  • Augmentation of safety in teleoperation system for intravascular neurosurgery: a new control strategy for force display based on the variable impedance characterization

    Page(s): 2890 - 2895 vol.4
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    A catheter is one of the medical tools for intravascular neurosurgeries. However, to control a catheter in narrow and complex blood vessels is a very difficult task, so there are not many surgeons who can operate a catheter appropriately. Moreover, these surgeons are exposed to X-ray radiation when they perform the operation. A solution to these problems is a telesurgery system. There are, however, some problems in telesurgery system. In this paper, we focus on the problem of operativity involved in a teleoperation system, and propose a new control strategy to display forces which are measured between a slave arm and the environment based on the variable impedance characterization of the master arm View full abstract»

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  • Robust path-following control with exponential stability for mobile robots

    Page(s): 3279 - 3284 vol.4
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    We present a new method for determining a path following controller for a nonholonomic mobile robot, which is robust with respect to position and orientation errors. We consider the kinematic model of a unicycle and dynamic extension. The control design is based on a change of variables allowing to define a set of n decoupled auxiliary variables. The exponential convergence of the state variables is deduced from the convergence of the auxiliary variables. We prove the control robustness by showing that, when the state variables measurement is noisy, the representative point of the system converges towards a compact attractive domain centred at the equilibrium point. As the auxiliary variables are decoupled, the computation of this attractive domain is done in a very simple and accurate way. The determination of such a domain can be used to determine a security margin to avoid obstacles during the path following process View full abstract»

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  • Antenna pointing for high bandwidth communications from mobile robots

    Page(s): 3468 - 3473 vol.4
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    This paper discusses the challenge of achieving high bandwidth, distant range wireless communication from mobile robots by way of antenna tracking. In the case of robots traversing rough terrain at moderate speeds, tracking demands high slew rates and large motion ranges due to vehicle motion disturbances. Attaining tracking accuracy, particular with the low mass and power inherent to mobile robots, requires an innovative approach. This paper presents the requirements analysis, mechanism design, sensor configuration and some experimental results for an antenna pointing mechanism that was developed for Nomad, a planetary-relevant mobile robot. The mechanism was demonstrated during the summer of 1997 in Nomad's 200 km traverse in the Atacama Desert of Chile View full abstract»

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  • Disturbance attenuation and load decoupling with H positive joint torque feedback

    Page(s): 3613 - 3618 vol.4
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    Positive joint torque feedback can compensate the detrimental effects of load torques on position tracking performance. However, with (real world) nonideal torque sources, simple unity gain positive torque feedback can actually deteriorate the performance, or even result in instability. An H joint torque feedback is proposed which takes the dynamics and uncertainty of the actuator into account and minimizes the system's sensitivity to load torques. In our experimental direct-drive system, the H positive torque feedback inner loop drastically improved the disturbance attenuation (25 dB) and load decoupling properties of a simple PID position controller View full abstract»

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  • Experiment design for robot dynamic calibration

    Page(s): 3303 - 3309 vol.4
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    Common robot calibration procedures use least-squares (LS) techniques to obtain estimates of the identifiable parameters. The “quality” of the resulting estimates depends significantly upon the used excitation input. The search for the best excitation trajectory is usually posed as a nonlinear path optimization problem aimed at optimizing suitable measures of the LS normal equations matrix. In this paper a parametrization of the class of reference joints trajectories is introduced and a solution framework based on genetic evolution is proposed. The efficiency of the method is illustrated by experimental tests on a SCARA two-link manipulator. Issues related to data acquisition and signals reconstruction and filtering are also discussed View full abstract»

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  • Biped robot walking using gravity-compensated inverted pendulum mode and computed torque control

    Page(s): 3528 - 3533 vol.4
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    This paper proposes a model called the gravity-compensated inverted pendulum mode (GCIPM) to generate a biped locomotion pattern that is similar to the one generated by the linear inverted pendulum mode, but accommodates the free leg dynamics based upon its predetermined trajectory. When the biped locomotion based upon the linear inverted pendulum mode is applied to real biped robots, the stability of the robot is disturbed due to the fact that the neglected dynamics of free legs is not actually negligible, moving the ZMP (zero moment point) away from the presumed fixed point. The GCIPM includes the effect of the dynamics of the free leg in a simple manner This paper also presents a control method for biped robots based upon the computed torque. Simulation results show that the biped robot is more stable with the walking pattern generated by the proposed method combined with the controller than with the one by the inverted pendulum mode View full abstract»

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  • Pipelined sampling techniques for sonar tracking systems

    Page(s): 2813 - 2818 vol.4
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    Introduces fast sampling strategies for pulse-echo time-of-flight sonar using time multiplexing. As a result, multiple interlaced measurement streams are employed to achieve high sampling rates without sacrificing range accuracy. The method considers receiver blanking constraints caused by imperfect acoustic decoupling between transmitter and receivers. Furthermore, uncertainties due to measurement noise and moving targets are taken into account. The proposed approach has been experimentally validated for sampling rates of up to 450 Hz with a multi sonar system mounted on a mobile robot View full abstract»

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  • Mobile robot exploration and map-building with continuous localization

    Page(s): 3715 - 3720 vol.4
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    Our research addresses how to integrate exploration and localization for mobile robots. A robot exploring and mapping an unknown environment needs to know its own location, but it may need a map in order to determine that location. In order to solve this problem, we have developed ARIEL, a mobile robot system that combines frontier based exploration with continuous localization. ARIEL explores by navigating to frontiers, regions on the boundary between unexplored space and space that is known to be open. ARIEL finds these regions in the occupancy grid map that it builds as it explores the world. ARIEL localizes by matching its recent perceptions with the information stored in the occupancy grid. We have implemented ARIEL on a real mobile robot and tested ARIEL in a real-world office environment. We present quantitative results that demonstrate that ARIEL can localize accurately while exploring, and thereby build accurate maps of its environment View full abstract»

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  • Detection of discrepancies and sensory-based recovery for virtual reality based telemanipulation systems

    Page(s): 2877 - 2883 vol.4
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    Teleoperators using an intermediate functional representation of the remote real environment (RE), suffer the lack of accurate synthetic modeling. Discrepancies will always occur between the RE and its artificial representation by means of virtual environment (VE). A strategy to deal with VE/RE uncertainties based mainly on sensory level interpretation is presented. It is directed to avoid the use of task knowledge by providing a stream of virtual sensors values. Within the remote site, a supervisor is in charge of recovering from the VE/RE discrepancies by a continuous simulated and real states comparison. The states are derived from simulated and real sensor interpretations respectively. A simple experiment with the proposed approach is presented using only position (velocity) and force sensors. Limitations of the proposed approach are also discussed View full abstract»

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  • Range data merging for probabilistic octree modeling of 3D workspaces

    Page(s): 3071 - 3078 vol.4
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    In a previous paper by Payeur et al. (1997), probabilistic occupancy modeling has been successfully extended to 3D environments by means of a closed-form approximation of the probability distribution. In this paper, the closed-form approximation is revisited in order to provide more reliable and meaningful models. A merging strategy of local probabilistic occupancy grids originating from each sensor viewpoint is introduced. The merging process takes advantage of the multiresolution characteristics of octrees to minimize the computational complexity and enhance performances. An experimental testbed is used to validate the approach and models computed from real range images are presented View full abstract»

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  • Study on cooperative positioning system: optimum moving strategies for CPS-III

    Page(s): 2896 - 2903 vol.4
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    This paper proposes a new method called “cooperative positioning system” (CPS) for mobile robots position identification. The main concept of CPS is to divide the robots into two groups, A and B respectively Group A remains stationary and acts as a landmark while group B is moving; group B then stops and acts as a landmark for group A. This process is repeated until the target position is reached. Compared with dead reckoning, CPS has a far lower accumulation of positioning error, and can also work in three-dimensions. Furthermore, CPS employs inherent landmarks and therefore can be used in uncharted environments unlike the landmark method. This paper focuses on the the relationship between moving configurations of CPS and its positioning accuracy for the latest prototype CPS model, CPS-III, using simulation and analytical techniques. Optimum moving strategies in order to minimize the positioning error are then discussed and verified through experiments View full abstract»

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  • A practical approach to feedback control for a mobile robot with trailer

    Page(s): 3291 - 3296 vol.4
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    This paper presents a robust method to control a mobile robot towing a trailer. Both problems of trajectory tracking and steering to a given configuration are addressed. This second issue is solved by an iterative trajectory tracking. Perturbations are taken into account along the motions. Experimental results on the mobile robot Hilare illustrate the validity of our approach View full abstract»

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  • Optimal 3D viewing with adaptive stereo displays

    Page(s): 3192 - 3197 vol.4
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    An optimal projection of stereo images onto an HMD screen is presented, such that the viewer can observe a real-world object or local scene of his/her interest in 3D, with the feeling of desired depth and scaling, under the minimum distortion. Taking the object or local scene of viewer's focal point as that of his/her interest, the proposed 3D viewing is intended to march the characteristics of human vision. The optimal projection is done by determining the scaling factor and horizontal displacement of the original stereo images as a function of the convergence angle of the stereo camera. In this paper, we put an emphasis on the verification of the proposed optimal 3D viewing method through experimentation View full abstract»

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  • Two methods for interpolating rigid body motions

    Page(s): 2922 - 2927 vol.4
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    This paper investigates methods for computing a smooth motion that interpolates a given set of positions and orientations of a rigid body. To make the interpolation independent of the representation of the motion, we use the coordinate-free framework of differential geometry. Inertial and body-fixed reference frames must be chosen to describe the position and orientation of the rigid body. We show that trajectories that are independent of the choice of these frames can be obtained by using the exponential map. Since these trajectories may exhibit rapid changes in velocity or its higher derivatives, a method for finding the maximally smooth interpolating curve is developed. Trajectories computed by both methods are compared on an example View full abstract»

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  • Localization algorithms: performance evaluation and reliability analysis

    Page(s): 3652 - 3657 vol.4
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    Workpiece localization plays a vital role in automation of many important manufacturing processes, such as workpiece setup, refixturing and dimensional inspection. In this paper, we provide a unified treatment of three geometric algorithms for workpiece localization, and develop new techniques to make these local algorithms globally convergent. We also study and analyze, along with extensive simulation results, their performance with respect to convergence and computational efficiency. Finally, we present a method for analyzing reliability of localization solutions and give a lower bound on the number of measurement points needed for reliable recovering of Euclidean transformations View full abstract»

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