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Robotics, IEEE Transactions on

Issue 5 • Date Oct. 2006

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Displaying Results 1 - 25 of 31
  • Table of contents

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  • IEEE Transactions on Robotics publication information

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  • Equivolumetric partition of solid spheres with applications to orientation workspace analysis of robot manipulators

    Page(s): 869 - 879
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (772 KB) |  | HTML iconHTML  

    Orientation workspace analysis is a critical issue in the design of robot manipulators, especially the spherical manipulators. However, there is a lack of effective methods for such analysis, because the orientation workspace of a robot manipulator is normally a subset of SO(3) (the special orthogonal group) with a complex boundary. Numerical approaches appear more practical in actual implementations. For numerical analysis, a finite partition of the orientation workspace in its parametric domain is necessary. It has been realized that the exponential coordinates parameterization is more appropriate for finite partition. With such a parameterization, the rigid body rotation group, i.e., SO(3), can be mapped to a solid sphere D3 of radius pi with antipodal points identified. A novel partition scheme is proposed to geometrically divide the parametric domain, i.e., the solid sphere D3 of radius pi, into finite elements with equal volume. Subsequently, the volume of SO(3) can be numerically computed as a weighted volume sum of the equivolumetric elements, in which the weightages are the element-associated integration measures. In this way, we can simplify the partition scheme and also reduce the computation efforts, as the elements in the same partition layer (along the radial direction) have the same integration measure. The effectiveness of the partition scheme is demonstrated through analysis of the orientation workspace of a three-degree-of-freedom spherical parallel manipulator. Numerical convergence on various orientation workspace measures, such as the workspace volume and the global condition index, are obtained based on this partition scheme View full abstract»

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  • Finding symmetric orthogonal Gough-Stewart platforms

    Page(s): 880 - 889
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    This paper develops new, analytical methods to find a large class of orthogonal Gough-Stewart platforms (OGSPs) having desired properties at their home position. In contrast, prior methods have been computationally intensive, relying on numerical search techniques. By exploiting symmetry, 27 equations are reduced to only two. The new techniques are directly applicable to clean-sheet design of micro-manipulators, vibration isolators, and Cartesian stiffness matrices. In addition, straightforward methods for retro-fitting existing OGSPs are illustrated. Because the new theory greatly simplifies OGSP formulas about a single point, it is expected that these results will also prove to be very useful when numerically designing gross motion platforms View full abstract»

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  • Wrench-feasible workspace generation for cable-driven robots

    Page(s): 890 - 902
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1356 KB) |  | HTML iconHTML  

    This paper presents a method for analytically generating the boundaries of the wrench-feasible workspace (WFW) for cable robots. This method uses the available net wrench set, which is the set of all wrenches that a cable robot can apply to its surroundings without violating tension limits in the cables. The geometric properties of this set permit calculation of the boundaries of the WFW for planar, spatial, and point-mass cable robots. Complete analytical expressions for the WFW boundaries are detailed for a planar cable robot and a spatial point-mass cable robot. The analytically determined boundaries are verified by comparison with numerical results. Based on this, several workspace properties are shown for point-mass cable robots. Finally, it is shown how this workspace-generation approach can be used to analytically formulate other workspaces View full abstract»

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  • Behavior-modulation technique in mobile robotics using fuzzy discrete event system

    Page(s): 903 - 916
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    This paper presents a novel behavior-modulation technique using a fuzzy discrete event system (FDES) for behavior-based robotic control. The method exploits the multivalued feature of fuzzy logic (FL) and event-driven property of a discrete event system (DES) to generate the activity of a behavior using fuzzy state vectors. State-based prediction of an activity is accomplished using fuzzily defined event matrices. A central arbiter employs priority-based arbitration among the activity state vectors and generates new event matrices to modify the activity states of the behaviors. The method combines aspects of both command fusion and behavior arbitration. Furthermore, the proposed approach has the ability to define state-based observability and controllability to handle sensory uncertainty and environmental dynamics. Observability describes decision vagueness associated with sensory data, whereas controllability specifies undesirable state-reach within the observed environment. Real-time results of FDES-based mobile robot navigation are presented and compared against four different modulation methods to validate its superior performance View full abstract»

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  • Optimal sensor scheduling for resource-constrained localization of mobile robot formations

    Page(s): 917 - 931
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (972 KB) |  | HTML iconHTML  

    This paper addresses the problem of resource allocation in formations of mobile robots localizing as a group. Each robot receives measurements from various sensors that provide relative (robot-to-robot) and absolute positioning information. Constraints on the sensors' bandwidth, as well as communication and processing requirements, limit the number of measurements that are available or can be processed at each time step. The localization uncertainty of the group, determined by the covariance matrix of the equivalent continuous-time system at steady state, is expressed as a function of the sensor measurements' frequencies. The trace of the weighted covariance matrix is selected as the optimization criterion, under linear constraints on the measuring frequency of each sensor and the cumulative rate of the extended Kalman filter updates. This formulation leads to a convex optimization problem (semidefinite program) whose solution provides the sensing frequencies, for each sensor on every robot, required in order to maximize the positioning accuracy of the group. Simulation and experimental results are presented that demonstrate the applicability of this method and provide insight into the properties of the resource-constrained cooperative localization problem View full abstract»

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  • Sensor data fusion for body state estimation in a hexapod robot with dynamical gaits

    Page(s): 932 - 943
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1292 KB) |  | HTML iconHTML  

    We report on a hybrid 12-dimensional full body state estimator for a hexapod robot executing a jogging gait in steady state on level terrain with regularly alternating ground contact and aerial phases of motion. We use a repeating sequence of continuous time dynamical models that are switched in and out of an extended Kalman filter to fuse measurements from a novel leg pose sensor and inertial sensors. Our inertial measurement unit supplements the traditionally paired three-axis rate gyro and three-axis accelerometer with a set of three additional three-axis accelerometer suites, thereby providing additional angular acceleration measurement, avoiding the need for localization of the accelerometer at the center of mass on the robot's body, and simplifying installation and calibration. We implement this estimation procedure offline, using data extracted from numerous repeated runs of the hexapod robot RHex (bearing the appropriate sensor suite) and evaluate its performance with reference to a visual ground-truth measurement system, comparing as well the relative performance of different fusion approaches implemented via different model sequences View full abstract»

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  • Design and control of tensegrity robots for locomotion

    Page(s): 944 - 957
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    The static properties of tensegrity structures have been widely appreciated in civil engineering as the basis of extremely lightweight yet strong mechanical structures. However, the dynamic properties and their potential utility in the design of robots have been relatively unexplored. This paper introduces robots based on tensegrity structures, which demonstrate that the dynamics of such structures can be utilized for locomotion. Two tensegrity robots are presented: TR3, based on a triangular tensegrity prism with three struts, and TR4, based on a quadrilateral tensegrity prism with four struts. For each of these robots, simulation models are designed, and automatic design of controllers for forward locomotion are performed in simulation using evolutionary algorithms. The evolved controllers are shown to be able to produce static and dynamic gaits in both robots. A real-world tensegrity robot is then developed based on one of the simulation models as a proof of concept. The results demonstrate that tensegrity structures can provide the basis for lightweight, strong, and fault-tolerant robots with a potential for a variety of locomotor gaits View full abstract»

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  • Stepping over obstacles with humanoid robots

    Page(s): 958 - 973
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3053 KB) |  | HTML iconHTML  

    The wide potential applications of humanoid robots require that the robots can walk in complex environments and overcome various obstacles. To this end, we address the problem of humanoid robots stepping over obstacles in this paper. We focus on two aspects, which are feasibility analysis and motion planning. The former determines whether a robot can step over a given obstacle, and the latter discusses how to step over, if feasible, by planning appropriate motions for the robot. We systematically examine both of these aspects. In the feasibility analysis, using an optimization technique, we cast the problem into global optimization models with nonlinear constraints, including collision-free and balance constraints. The solutions to the optimization models yield answers to the possibility of stepping over obstacles under some assumptions. The presented approach for feasibility provides not only a priori knowledge and a database to implement stepping over obstacles, but also a tool to evaluate and compare the mobility of humanoid robots. In motion planning, we present an algorithm to generate suitable trajectories of the feet and the waist of the robot using heuristic methodology, based on the results of the feasibility analysis. We decompose the body motion of the robot into two parts, corresponding to the lower body and upper body of the robot, to meet the collision-free and balance constraints. This novel planning method is adaptive to obstacle sizes, and is, hence, oriented to autonomous stepping over by humanoid robots guided by vision or other range finders. Its effectiveness is verified by simulations and experiments on our humanoid platform HRP-2 View full abstract»

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  • Controlled passive dynamic running experiments with the ARL-monopod II

    Page(s): 974 - 986
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1178 KB) |  | HTML iconHTML  

    This paper presents the expansion and implementation of the controlled passive dynamic running (CPDR) strategy for legged robots, previously presented by the authors. The CPDR exploits the underlying passive dynamic operation of the robot's mechanical systems to reduce the energy spent for locomotion. Meanwhile, it ensures the stability of the vertical and forward motions as the robot speed varies. An "adaptive energy controller" stabilizes the hopping height accurately over a range of operating conditions. The passive dynamic derivations for the Monopod, together with the foot-placement algorithm and model-based joint controllers, are used to control the forward speed about the passive operation trajectories. New locomotion variables are used for robust synchronization between the hip-body and the leg oscillations. ARL-Monopod II achieved a speed of 1.25 m/s with specific resistance (a measure for energy cost of locomotion) of 30% of the earlier robot ARL-Monopod I, its predecessor, due to the newer hip and leg design and application of the CPDR control strategy View full abstract»

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  • Real-time adaptive control for haptic telemanipulation with Kalman active observers

    Page(s): 987 - 999
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1189 KB) |  | HTML iconHTML  

    This paper discusses robotic telemanipulation with Kalman active observers and online stiffness estimation. Operational space techniques, feedback linearization, discrete state space methods, augmented states, and stochastic design are used to control a robotic manipulator with a haptic device. Stiffness estimation only based on force data (measured, desired, and estimated forces) is proposed, avoiding explicit position information. Stability and robustness to stiffness errors are discussed, as well as real-time adaptation techniques. Telepresence is analyzed. Experiments show high performance in contact with soft and hard surfaces View full abstract»

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  • Optimizing plane-to-plane positioning tasks by image-based visual servoing and structured light

    Page(s): 1000 - 1010
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (872 KB) |  | HTML iconHTML  

    This paper considers the problem of positioning an eye-in-hand system so that it becomes parallel to a planar object. Our approach to this problem is based on linking to the camera a structured light emitter designed to produce a suitable set of visual features. The aim of using structured light is not only for simplifying the image processing and allowing low-textured objects to be considered, but also for producing a control scheme with nice properties like decoupling, convergence, and adequate camera trajectory. This paper focuses on an image-based approach that achieves decoupling in all the workspace, and for which the global convergence is ensured in perfect conditions. The behavior of the image-based approach is shown to be partially equivalent to a 3-D visual servoing scheme, but with a better robustness with respect to image noise. Concerning the robustness of the approach against calibration errors, it is demonstrated both analytically and experimentally View full abstract»

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  • Analytical determination of the workspace of symmetrical spherical parallel mechanisms

    Page(s): 1011 - 1017
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2478 KB) |  | HTML iconHTML  

    This paper presents a methodology for the analytical determination and representation of the workspace boundaries of symmetrical spherical parallel mechanisms (SPMs). The methodology is based on an intuitive orientation representation which, while not well known, has proven to be very useful for the analysis of symmetrical parallel mechanisms. The latter, previously introduced as "tilt-and-torsion angles," are briefly described. Then, relatively simple analytical expressions are found for the workspace boundaries of general symmetrical SPMs. Next, using these expressions and a simple numerical procedure, a fast algorithm is proposed for representing the so-called constant-torsion workspace. Finally, several examples are provided View full abstract»

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  • Fault tolerance of parallel manipulators using task space and kinematic redundancy

    Page(s): 1017 - 1021
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    When a parallel manipulator suffers from failures, its performance can be significantly affected. Thus, fault tolerance is essential for task-critical applications or applications in which maintenance is hard to implement. In this paper, we consider three types of common strut failures corresponding to stuck joints, unactuated actuators, or the complete loss of struts, respectively. The impacts of different failures on the kinematics of a manipulator are examined, and the task space redundancy and kinematic redundancies are used to help overcome these failures. In addition, local measures of fault tolerance and their properties are analyzed. These measures can be helpful in architecture design and path planning View full abstract»

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  • A new index of serial-link manipulator performance combining dynamic manipulability and manipulating force ellipsoids

    Page(s): 1022 - 1028
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    The inertia matching ellipsoid (IME) is proposed as a new index of dynamic performance for serial-link robotic manipulators. The IME integrates the existing dynamic manipulability and manipulating-force ellipsoids to achieve an accurate measure of the dynamic torque-force transmission efficiency between the joint torque and the force applied to a load held by an end-effector. The dynamic manipulability and manipulating-force ellipsoids can both be derived from the IME as limiting forms, with respect to the weight of the load. The effectiveness of the IME is demonstrated numerically through the selection of an optimal leg posture for jumping robots and optimal active stiffness control, and experimentally through application to a pick-up task using a commercial manipulator. The index is also extended theoretically to the case of a manipulator mounted on a free-flying satellite View full abstract»

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  • Online task recognition and real-time adaptive assistance for computer-aided machine control

    Page(s): 1029 - 1033
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    Segmentation and recognition of operator-generated motions are commonly facilitated to provide appropriate assistance during task execution in teleoperative and human-machine collaborative settings. The assistance is usually provided in a virtual fixture framework where the level of compliance can be altered online, thus improving the performance in terms of execution time and overall precision. However, the fixtures are typically inflexible, resulting in a degraded performance in cases of unexpected obstacles or incorrect fixture models. In this paper, we present a method for online task tracking and propose the use of adaptive virtual fixtures that can cope with the above problems. Here, rather than executing a predefined plan, the operator has the ability to avoid unforeseen obstacles and deviate from the model. To allow this, the probability of following a certain trajectory (subtask) is estimated and used to automatically adjusts the compliance, thus providing the online decision of how to fixture the movement View full abstract»

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  • Acquisition of intermediate goals for an agent executing multiple tasks

    Page(s): 1034 - 1040
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    In this paper, an algorithm that acquires the intermediate goals between the initial and goal states is proposed for an agent executing multiple tasks. We demonstrate the algorithm in the problem of rearranging multiple objects. The result shows that the moving distance to transfer the entire objects to their goal configuration is 1/15 of that without using intermediate goals. We experiment using a real robot to confirm that the intermediate goal can be adapted to a real environment. Our experimental results showed that an agent could adapt the intermediate goals, which were acquired in the simulation, to the experimental environment View full abstract»

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  • Nonholonomic distance to polygonal obstacles for a car-like robot of polygonal shape

    Page(s): 1040 - 1047
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (443 KB) |  | HTML iconHTML  

    This paper shows how to compute the nonholonomic distance between a polygonal car-like robot and polygonal obstacles. The solution extends previous work of Reeds and Shepp by finding the shortest path to a manifold (rather than to a point) in configuration space. Based on optimal control theory, the proposed approach yields an analytic solution to the problem View full abstract»

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  • Metric-based iterative closest point scan matching for sensor displacement estimation

    Page(s): 1047 - 1054
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (889 KB) |  | HTML iconHTML  

    This paper addresses the scan matching problem for mobile robot displacement estimation. The contribution is a new metric distance and all the tools necessary to be used within the iterative closest point framework. The metric distance is defined in the configuration space of the sensor, and takes into account both translation and rotation error of the sensor. The new scan matching technique ameliorates previous methods in terms of robustness, precision, convergence, and computational load. Furthermore, it has been extensively tested to validate and compare this technique with existing methods View full abstract»

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  • Modeling and hierarchical tracking control of tri-wheeled mobile robots

    Page(s): 1055 - 1062
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    After exploring the structure of the dynamics derived by using the Appell equation, we propose a hierarchical tracking controller for a tri-wheeled mobile robot in this paper. With appropriately chosen privileged variables, the reduced equations are decoupled from the kinematic equations associated with the underlying nonholonomic constraints. This special character of the system makes it possible to separate the design into three levels: motion planning, kinematic, and dynamic. In the proposed scheme, a fuzzy inference engine in the kinematic level is used to update the desired trajectory computed in the motion-planning level. An adaptive sliding-mode controller is then adopted to track the new reference values of privileged variables in the dynamic level, which subsequently drives the nonprivileged variables. Simulation results show the effectiveness of such a tracking-control scheme, which concurrently takes kinematics and dynamics into consideration. All system variables can be tracked asymptotically to their desired values, which are assured by the skew-symmetric property of the Appell equation View full abstract»

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  • Stability analysis of a vision-based control design for an autonomous mobile robot

    Page(s): 1062 - 1069
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    We propose a simple control design allowing a mobile robot equipped with a camera to track a line on the ground. The control algorithm, as well as the image-processing algorithm, are very simple. We discuss the existence and the practical stability of an equilibrium trajectory of the robot when tracking a circular reference line. We then give a complementary analysis for arbitrary reference lines with bounded curvature. Experimental results confirm the theoretical analysis View full abstract»

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  • In this issue

    Page(s): 1070
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  • Special issue on bio-robotics

    Page(s): 1071
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    Freely Available from IEEE
  • Special issue on drug delivery automation

    Page(s): 1072
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Aims & Scope

IEEE Transactions on Robotics covers both theory and applications on topics including: kinematics, dynamics, control, and simulation of robots and intelligent machines and systems.

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Meet Our Editors

Editor-in-Chief
Frank Park
Seoul National University