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Robotics, IEEE Transactions on

Issue 4 • Date Aug. 2011

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Displaying Results 1 - 24 of 24
  • Table of contents

    Page(s): C1
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  • IEEE Transactions on Robotics publication information

    Page(s): C2
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  • Discrete Geometric Optimal Control on Lie Groups

    Page(s): 641 - 655
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (828 KB) |  | HTML iconHTML  

    We consider the optimal control of mechanical systems on Lie groups and develop numerical methods that exploit the structure of the state space and preserve the system motion invariants. Our approach is based on a coordinate-free variational discretization of the dynamics that leads to structure-preserving discrete equations of motion. We construct necessary conditions for optimal trajectories that correspond to discrete geodesics of a higher order system and develop numerical methods for their computation. The resulting algorithms are simple to implement and converge to a solution in very few iterations. A general software implementation is provided and applied to two example systems: an underactuated boat and a satellite with thrusters. View full abstract»

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  • Parameterization and Evaluation of Robotic Orientation Workspace: A Geometric Treatment

    Page(s): 656 - 663
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (345 KB) |  | HTML iconHTML  

    The volume of the orientation workspace is measured based on two invariant principles: It must be invariant with respect to the ground frame and invariant with respect to the orientation description. A method which is based on quaternions and differential geometry is developed for the measurement of the volume correctly. The method is extended for an arbitrary orientation description by means of a mapping theorem proposed for the first time. An example of a serial spherical wrist shows that the volumes that are obtained by the proposed method are consistent with the two invariant principles. View full abstract»

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  • A Nonlinear Attitude Observer Based on Active Vision and Inertial Measurements

    Page(s): 664 - 677
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1837 KB) |  | HTML iconHTML  

    This paper presents an experimentally evaluated solution to the problem of estimating the attitude of a rigid body using rate gyros and a pan-tilt camera. A nonlinear attitude observer combines angular velocity measurements obtained from rate gyros with images of a planar scene provided by the camera. By directly exploiting the sensor information, a stabilizing feedback law is introduced, and exponential convergence to the origin of the estimation errors is shown. Additionally, an active-vision system is proposed that relies on an image-based exponentially input-to-state-stable control law for the pan and tilt angular rates of the camera to keep the features in the image plane. Using recent results in geometric numerical integration, a multirate implementation of the observer is proposed, which exploits the complementary bandwidth of the sensors. Practical considerations, such as the lens-distortion compensation and the computation of suitable observer feedback gains, are considered. Experimental results obtained with a high-accuracy motion rate table demonstrate the high level of performance attained by the proposed solution. View full abstract»

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  • Multirobot Active Target Tracking With Combinations of Relative Observations

    Page(s): 678 - 695
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1451 KB) |  | HTML iconHTML  

    In this paper, we study the problem of optimal trajectory generation for a team of heterogeneous robots moving in a plane and tracking a moving target by processing relative observations, i.e., distance and/or bearing. Contrary to previous approaches, we explicitly consider limits on the robots' speed and impose constraints on the minimum distance at which the robots are allowed to approach the target. We first address the case of a single tracking sensor and seek the next sensing location in order to minimize the uncertainty about the target's position. We show that although the corresponding optimization problem involves a nonconvex objective function and a nonconvex constraint, its global optimal solution can be determined analytically. We then extend the approach to the case of multiple sensors and propose an iterative algorithm, i.e., the Gauss-Seidel relaxation (GSR), to determine the next best sensing location for each sensor. Extensive simulation results demonstrate that the GSR algorithm, whose computational complexity is linear in the number of sensors, achieves higher tracking accuracy than gradient descent methods and has performance that is indistinguishable from that of a grid-based exhaustive search, whose cost is exponential in the number of sensors. Finally, through experiments, we demonstrate that the proposed GSR algorithm is robust and applicable to real systems. View full abstract»

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  • The Hybrid Reciprocal Velocity Obstacle

    Page(s): 696 - 706
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (990 KB) |  | HTML iconHTML  

    We present the hybrid reciprocal velocity obstacle for collision-free and oscillation-free navigation of multiple mobile robots or virtual agents. Each robot senses its surroundings and acts independently without central coordination or communication with other robots. Our approach uses both the current position and the velocity of other robots to compute their future trajectories in order to avoid collisions. Moreover, our approach is reciprocal and avoids oscillations by explicitly taking into account that the other robots sense their surroundings as well and change their trajectories accordingly. We apply hybrid reciprocal velocity obstacles to iRobot Create mobile robots and demonstrate direct, collision-free, and oscillation-free navigation. View full abstract»

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  • Multirobot Tree and Graph Exploration

    Page(s): 707 - 717
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1422 KB) |  | HTML iconHTML  

    In this paper, we present an algorithm for the exploration of an unknown graph by multiple robots, which is never worse than depth-first search with a single robot. On trees, we prove that the algorithm is optimal for two robots. For k robots, the algorithm has an optimal dependence on the size of the tree but not on its radius. We believe that the algorithm performs well on any tree, and this is substantiated by simulations. For trees with e edges and radius r, the exploration time is less than 2e/k + (1 + (k/r))k-1 (2/k!)rk-1 = (2e/k) + O((k + r)k-1) (for r >; k, <; (2e/k) + 2rk-1), thereby improving a recent method with time O((e/logk) + r) [2], and almost reaching the lower bound max((2e/k), 2r). The model underlying undirected-graph exploration is a set of rooms connected by opaque passages; thus, the algorithm is appropriate for scenarios like indoor navigation or cave exploration. In this framework, communication can be realized by bookkeeping devices being dropped by the robots at explored vertices, the states of which are read and changed by further visiting robots. Simulations have been performed in both tree and graph explorations to corroborate the mathematical results. View full abstract»

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  • Programmable Assembly With Universally Foldable Strings (Moteins)

    Page(s): 718 - 729
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    Understanding how linear strings fold into 2-D and 3-D shapes has been a long sought goal in many fields of both academia and industry. This paper presents a technique to design self-assembling and self-reconfigurable systems that are composed of strings of very simple robotic modules. We show that physical strings that are composed of a small set of discrete polygonal or polyhedral modules can be used to programmatically generate any continuous area or volumetric shape. These modules can have one or two degrees of freedom (DOFs) and simple actuators with only two or three states. We describe a subdivision algorithm to produce universal polygonal and polyhedral string folding schemas, and we prove the existence of a continuous motion to reach any such folding. This technique is validated with dynamics simulations as well as experiments with chains of modules that pack on a regular cubic lattice. We call robotic programmable universally foldable strings “moteins” as motorized proteins. View full abstract»

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  • Haptic Interactions Using Virtual Manipulator Coupling With Applications to Underactuated Systems

    Page(s): 730 - 740
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1070 KB) |  | HTML iconHTML  

    Haptic interactions have become increasingly important as an interface to computer-generated simulations in virtual-reality (VR) applications. Many haptic devices are designed to be used as a force feedback mouse, where the user's hand is in contact with the haptic device while the object contact and force generation occur on a computer screen. In this paper, we present an approach using a “virtual probe” to interact with the environment and introduce a new method to generate impedance-based haptic forces based on the use of a virtual manipulator. The virtual probe is connected directly to the haptic device and is projected from the hand to the environment, much like a scalpel or sword. As the probe comes in contact with the environment, the haptic device generates appropriate forces on the hand. We extend this approach to include underactuated haptic devices, which do not have fully powered joints. We show that the approach compensates for missing joint actuation in the underactuated haptic devices. We show experimental results for a simple case of haptic interaction; we also present an experimental implementation in six degrees of freedom (DOF) using one of the most popular devices: the PHANTOM. View full abstract»

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  • Bilateral Telemanipulation With Time Delays: A Two-Layer Approach Combining Passivity and Transparency

    Page(s): 741 - 756
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1219 KB) |  | HTML iconHTML  

    In this paper, a two-layer approach is presented to guarantee the stable behavior of bilateral telemanipulation systems in the presence of time-varying destabilizing factors such as hard contacts, relaxed user grasps, stiff control settings, and/or communication delays. The approach splits the control architecture into two separate layers. The hierarchical top layer is used to implement a strategy that addresses the desired transparency, and the lower layer ensures that no “virtual” energy is generated. This means that any bilateral controller can be implemented in a passive manner. Separate communication channels connect the layers at the slave and master sides so that information related to exchanged energy is completely separated from information about the desired behavior. Furthermore, the proposed implementation does not depend on any type of assumption about the time delay in the communication channel. By complete separation of the properties of passivity and transparency, each layer can accommodate any number of different implementations that allow for almost independent optimization. Experimental results are presented, which highlight the benefit of the proposed framework. View full abstract»

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  • Active Stabilization for Robotized Beating Heart Surgery

    Page(s): 757 - 768
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1240 KB) |  | HTML iconHTML  

    In this paper, control strategies for an active stabilizer dedicated to beating heart coronary artery bypass grafting are investigated. The active stabilizer, which consists of a piezoactuated compliant mechanism, has to be controlled to compensate for the displacements induced by the beating heart in order to provide the surgeon with a locally motionless myocardium surface. Three controllers, including different levels of prior knowledge about the heart motion, are presented. Their performance with respect to modeling uncertainties, arising unknown interactions of the stabilizer with its positioning mechanism, and the heart, is studied through simulations, as well as laboratory and in vivo experiments. Finally, the selection of the most adequate control scheme and the performance of the device from a clinical point of view are discussed. View full abstract»

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  • A Novel Magnetic Actuation System for Miniature Swimming Robots

    Page(s): 769 - 779
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    A novel mechanism for actuating a miniature swimming robot is described, modeled, and experimentally validated. Underwater propulsion is obtained through the interaction of mobile internal permanent magnets that move a number of polymeric flaps arranged around the body of the robot. Due to the flexibility of the proposed swimming mechanism, a different range of performances can be obtained by varying the design features. A simple multiphysics dynamic model was developed in order to predict basic behavior in fluids for different structural parameters of the robot. In order to experimentally verify the proposed mechanism and to validate the model, a prototype of the swimming robot was fabricated. The device is 35 mm in length and 18 mm in width and thickness, and the forward motion is provided by four flaps with an active length of 20 mm. The model was able to correctly predict flap dynamics, thrust, and energy expenditure for magnetic dragging within a spindle-frequency range going from 2 to 5 Hz. Additionally, the model was used to infer robot-thrust variation related to different spindle frequencies and a 25% increase in flap active length. Concerning swimming performance, the proposed technical implementation of the concept was able to achieve 37 mm/s with 4.9% magnetic mechanism efficiency. View full abstract»

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  • On the Stability of Closed-Loop Inverse Kinematics Algorithms for Redundant Robots

    Page(s): 780 - 784
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB) |  | HTML iconHTML  

    The purpose of this paper is to provide a convergence analysis of classical inverse kinematics algorithms for redundant robots, whose stability is usually proved only in the continuous-time domain, thus neglecting limits of the actual implementation in the discrete time, whereas the convergence analysis carried out in this paper in the discrete-time domain provides a method to find bounds on the gain of the closed-loop inverse kinematics algorithms in relation to the sampling time. It also provides an estimation of the region of attraction (without resorting to Lyapunov arguments), i.e., upper bounds on the initial task space error. Simulations on an 11-degree-of-freedom manipulator are performed to show how the found bounds on the gain are not too restrictive. View full abstract»

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  • Kinematic Control of Redundant Manipulators: Generalizing the Task-Priority Framework to Inequality Task

    Page(s): 785 - 792
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (585 KB) |  | HTML iconHTML  

    Redundant mechanical systems like humanoid robots are designed to fulfill multiple tasks at a time. A task, in velocity-resolved inverse kinematics, is a desired value for a function of the robot configuration that can be regulated with an ordinary differential equation (ODE). When facing simultaneous tasks, the corresponding equations can be grouped in a single system or, better, sorted in priority and solved each in the solutions set of higher priority tasks. This elegant framework for hierarchical task regulation has been implemented as a sequence of least-squares problems. Its limitation lies in the handling of inequality constraints, which are usually transformed into more restrictive equality constraints through potential fields. In this paper, we propose a new prioritized task-regulation framework based on a sequence of quadratic programs (QP) that removes the limitation. At the basis of the proposed algorithm, there is a study of the optimal sets resulting from the sequence of QPs. The algorithm is implemented and illustrated in simulation on the humanoid robot HRP-2. View full abstract»

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  • Experimental Investigation of Obstacle-Aided Locomotion With a Snake Robot

    Page(s): 792 - 800
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1444 KB) |  | HTML iconHTML  

    In a recent paper, the authors have proposed a control strategy for a snake robot during obstacle-aided locomotion. In this paper, experimental results are presented where the controller is shown to successfully maintain the forward propulsion of a physical snake robot in a course with different obstacle configurations. View full abstract»

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  • Minimum-Time Trajectory for Three-Wheeled Omnidirectional Mobile Robots Following a Bounded-Curvature Path With a Referenced Heading Profile

    Page(s): 800 - 808
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (961 KB) |  | HTML iconHTML  

    The minimum-time trajectory planning problem for three-wheeled omnidirectional mobile robots (TOMRs) is solved based on the combined dynamic model of a mobile robot and dc motor actuators, under the constraint of bounded control inputs due to the battery voltage. We constrain that the bounded-curvature path based on a smooth road (which is described as a clothoid) be given for the translational motion of the TOMR and that the reference profile with respect to the path-length parameter be predetermined for the heading motion of the TOMR. The dynamics of the TOMR is transformed into normal and tangent spaces for motion analysis on the bounded-curvature path. We find out the time-optimality condition of the TOMR, which imposes that the input voltage vector of three motors should have at least one extreme component. Based on the optimality condition, we present a systematic way to construct the optimal control input vector. Finally, several examples are analyzed by the use of the proposed method. View full abstract»

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  • Probabilistic Collision Checking With Chance Constraints

    Page(s): 809 - 815
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (449 KB) |  | HTML iconHTML  

    Obstacle avoidance, and by extension collision checking, is a basic requirement for robot autonomy. Most classical approaches to collision-checking ignore the uncertainties associated with the robot and obstacle's geometry and position. It is natural to use a probabilistic description of the uncertainties. However, constraint satisfaction cannot be guaranteed, in this case, and collision constraints must instead be converted to chance constraints. Standard results for linear probabilistic constraint evaluation have been applied to probabilistic collision evaluation; however, this approach ignores the uncertainty associated with the sensed obstacle. An alternative formulation of probabilistic collision checking that accounts for robot and obstacle uncertainty is presented which allows for dependent object distributions (e.g., interactive robot-obstacle models). In order to efficiently enforce the resulting collision chance constraints, an approximation is proposed and the validity of this approximation is evaluated. The results presented here have been applied to robot-motion planning in dynamic, uncertain environments. View full abstract»

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  • Modeling and Evaluation of Low-Cost Force Sensors

    Page(s): 815 - 822
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (829 KB) |  | HTML iconHTML  

    Low-cost piezoresistive sensors can be of great interest in robotic applications due not only to their advantageous cost but to their dimension as well, which enables an advanced mechanical integration. In this paper, a comparison of two commercial piezoresistive sensors based on different technologies is performed in the case of a medical robotics application. The existence of significant nonlinearities in their dynamic behavior is demonstrated, and a nonlinear modeling is proposed. A compensation scheme is developed for the sensor with the largest nonlinearities before discussing the selection of a sensor for dynamic applications. It is shown that force control is achievable with these kinds of sensors, in spite of their drawbacks. Experiments with both types of sensors are presented, including force control with a medical robot. View full abstract»

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  • Keeping Multiple Moving Targets in the Field of View of a Mobile Camera

    Page(s): 822 - 828
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (441 KB) |  | HTML iconHTML  

    This study introduces a novel visual servo controller that is designed to control the pose of the camera to keep multiple objects in the field of view (FOV) of a mobile camera. In contrast with other visual servo methods, the control objective is not formulated in terms of a goal pose or a goal image. Rather, a set of underdetermined task functions are developed to regulate the mean and variance of a set of image features. Regulating these task functions inhibits feature points from leaving the camera FOV. An additional task function is used to maintain a high level of motion perceptibility, which ensures that desired feature point velocities can be achieved. These task functions are mapped to camera velocity, which serves as the system input. A proof of stability is presented for tracking three or fewer targets. Experiments of tracking eight or more targets have verified the performance of the proposed method. View full abstract»

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  • Photometric Visual Servoing

    Page(s): 828 - 834
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (814 KB) |  | HTML iconHTML  

    This paper proposes a new way to achieve robotic tasks by two-dimensional (2-D) visual servoing. Indeed, instead of using classical geometric features such as points, straight lines, pose, or a homography, as is usually done, the luminance of all pixels in the image is considered here. The main advantage of this new approach is that it requires no tracking or matching process. The key point of our approach relies on the analytic computation of the interaction matrix. This computation is based either on a temporal luminance-constancy hypothesis or on a reflection model so that complex illumination changes can be considered. Experimental results on positioning and tracking tasks validate the proposed approach and show its robustness to approximated depths, low-textured objects, partial occlusions, and specular scenes. They also showed that luminance leads to lower positioning errors than a classical visual servoing based on 2-D geometric visual features. View full abstract»

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  • IEEE copyright form

    Page(s): 835 - 836
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  • IEEE Robotics and Automation Society Information

    Page(s): C3
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  • IEEE Transactions on Robotics Information for authors

    Page(s): C4
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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