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Robotics and Automation, IEEE Transactions on

Issue 6 • Date Dec 1993

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Displaying Results 1 - 18 of 18
  • Design of a singularity-free articulated arm subassembly

    Page(s): 816 - 824
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    Adding a redundant degree of freedom to the shoulder pointing system complex of an articulated arm subassembly makes it possible to achieve a maximal workspace that is free of singularities. This paper derives a functional constraint between three of the four joints of this new type of arm, achieving a singularity-free workspace encompassing the entire reachable volume between the maximal- and minimal-reach surfaces. The large volume of dexterous workspace is verified by animation of the resulting arm design. Graphical results from the animation are presented comparing the dexterous workspace of this new arm to that of the standard nonredundant articulated arm subassembly found in the Puma manipulator View full abstract»

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  • Position and constraint force control of a vehicle with two or more steerable drive wheels

    Page(s): 723 - 731
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    Since a vehicle with two or more steerable drive wheels is always traveling in a circle about an instantaneous center of rotation, the motion of the wheels is constrained. The wheel translational velocity divided by the radius to the center of rotation must be the same for all wheels. When the drive wheels are controlled independently using position control, the motion of the wheels may violate the constraints and the wheels may slip. Consequently, substantial errors can occur in the position and orientation of the vehicle. A vehicle with N steerable drive wheels has N holonomic constraints on the steering angles, (N-1) nonholonomic constraints on the wheel velocities, and one degree of freedom. The authors have developed a new approach to the control of a vehicle with N steerable drive wheels. The novel aspect of their approach is the introduction of variables to control the constraint forces. To control the vehicle, the authors have one variable to control motion and (N-1) variables that can control the constraint forces to reduce errors. Kankaanranta and Koivo (1988) developed a control architecture that allows the control variables for force and position to be decoupled. In the work of Kankaaranta and Koivo the control variables for force are an exogenous input. The authors have made the central variables for force endogenous by defining them in terms of the errors in satisfying the nonholonomic constraints. The authors have applied the control architecture to the HERMIES-III robot and have measured a dramatic reduction in error (more than a factor of 20) compared to motions without constraint force control View full abstract»

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  • Vectorization of robot inverse dynamics on a pipelined vector processor

    Page(s): 858 - 863
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    This paper presents a computational scheme on a pipelined vector processor for robot inverse dynamics. Vectorization of the inverse dynamics computation is achieved while the dynamics formulation still remains within the general linear recursive framework. Parametric studies are conducted on a commercially available pipelined vector processor. The 1.82 speedup is achieved through vectorization for the inverse dynamics computation of a general six-degrees-of-freedom robot manipulator View full abstract»

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  • Motion planning in stereotaxic radiosurgery

    Page(s): 764 - 774
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    Stereotaxic radiosurgery is a procedure that uses a beam of radiation as an ablative surgical instrument to destroy brain tumors (or more generally, brain lesions). The beam is produced by a linear accelerator that is moved by a mechanical gantry. Radiation is concentrated by crossfiring at the tumor from multiple directions, to reduce the amount of energy deposited in healthy tissues. Because access to and exit from the tumor is obstructed along some directions by critical structures (e.g., brain stem, optic nerves), planning the path of the beam is often difficult and time-consuming. This paper describes a computer-based planner developed to interactively assist the surgeon generate a satisfactory treatment, given the spatial distribution of the brain tissues obtained with medical imaging. This planner has been experimented on using 11 cases previously processed at the Stanford Medical Center. A dosimetric comparison with the manually generated plans for these cases was carried but. Although still limited, results indicate that automatic planning can significantly improve energy deposition. It can also shorten the overall treatment, hence reducing the patient's pain and allowing the radiosurgery equipment to be used for more patients. Stereotaxic radiosurgery is an example of so-called “bloodless surgery.” Computer-based planning techniques are expected to facilitate further development of this safer, less painful, and more cost effective type of surgery View full abstract»

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  • A passivity approach to controller-observer design for robots

    Page(s): 740 - 754
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    Passivity-based control methods for robots, which achieve the control objective by reshaping the robot system's natural energy via state feedback, have, from a practical point of view, some very attractive properties. However, the poor quality of velocity measurements may significantly deteriorate the control performance of these methods. In this paper the authors propose a design strategy that utilizes the passivity concept in order to develop combined controller-observer systems for robot motion control using position measurements only. To this end, first a desired energy function for the closed-loop system is introduced, and next the controller-observer combination is constructed such that the closed-loop system matches this energy function, whereas damping is included in the controller- observer system to assure asymptotic stability of the closed-loop system. A key point in this design strategy is a fine tuning of the controller and observer structure to each other, which provides solutions to the output-feedback robot control problem that are conceptually simple and easily implementable in industrial robot applications. Experimental tests on a two-DOF manipulator system illustrate that the proposed controller-observer systems enable the achievement of higher performance levels compared to the frequently used practice of numerical position differentiation for obtaining a velocity estimate View full abstract»

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  • Representation and learning of nonlinear compliance using neural nets

    Page(s): 863 - 867
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    A new approach to compliant motion control using neural networks is presented. In the paper, “compliance” is treated as a nonlinear mapping from a measured force to a corrected motion. The nonlinear mapping by a multilayer neural network is outlined, this allows one to deal with complex control strategies that cannot be represented by linear compliance, such as in stiffness and damping control View full abstract»

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  • On the inertia duality of parallel-series connections of two robots in operational space

    Page(s): 846 - 854
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    The inertias of the parallel and serial connections of two robots in the operational space are studied in this paper. First, it is reviewed that the symmetry between the velocity and force in a robotic chain results in velocity-force duality of the parallel and serial connections. The possible duality in the operational inertia matrix is then investigated. From the dynamic equations of the two connections, it is found that there does not exist a real duality in the operational inertia matrix. However, the real duality becomes possible when the coupling effects between the two robots are negligible. This conditional duality is called “quasi-duality” in this paper. As a result of this study, the duality behaviors of the two connections in velocity, force and inertia are completely obtained View full abstract»

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  • A robust adaptive robot controller

    Page(s): 825 - 830
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    A globally convergent adaptive control scheme for robot motion control with the following features is proposed. First, the adaptation law possesses enhanced robustness with respect to noisy velocity measurements. Second, the controller does not require the inclusion of high gain loops that may excite the unmodeled dynamics and amplify the noise level. Third, we derive for the unknown parameter design a relationship between compensator gains and closed-loop convergence rates that is independent of the robot task. A simulation example of a two-DOF manipulator featuring some aspects of the control scheme is given View full abstract»

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  • Significant line segments for an indoor mobile robot

    Page(s): 801 - 815
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    New algorithms for detecting and interpreting linear features of a real scene as imaged by a single camera on a mobile robot are described. The low-level processing stages are specifically designed to increase the usefulness and the quality of the extracted features for indoor scene understanding. In order to derive 3-D information from a 2-D image, we consider only lines with particular orientation in 3-D. The detection and interpretation processes provide a 3-D orientation hypothesis for each 2-D segment. This in turn is used to estimate the robot's orientation and relative position in the environment. Next, the orientation data is used by a motion stereo algorithm to fully estimate the 3-D structure when a sequence of images becomes available. From detection to 3-D estimation, a strong emphasis is placed on real-world applications and very fast processing with conventional hardware. Results of experimentation with a mobile robot under realistic conditions are given and discussed View full abstract»

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  • Optimal robust path planning in general environments

    Page(s): 775 - 784
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1136 KB)  

    We address robust path planning for a mobile agent in a general environment by finding minimum cost source-destination paths having prescribed widths. The main result is a new approach that optimally solves the robust path planning problem using an efficient network flow formulation. Our algorithm represents a significant departure from conventional shortest-path or graph search based methods; it not only handles environments with solid polygonal obstacles, but also generalizes to arbitrary cost maps that may arise in modeling incomplete or uncertain knowledge of the environment. Simple extensions allow us to address higher dimensional problem instances and minimum-surface computations; the latter is a result of independent interest. We use an efficient implementation to exhibit optimal path-planning solutions for a variety of test problems. The paper concludes with open issues and directions for future work View full abstract»

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  • Controllability of a multibody mobile robot

    Page(s): 755 - 763
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    This paper presents a proof of controllability for a multibody mobile robot (e.g., a car pulling and pushing trailers like a luggage carrier in an airport). Such systems appear as canonical systems to illustrate the tools from differential geometric control theory required by nonholonomic motion planning. Three modeling steps are considered: geometric, differential, and control steps. The author derives the kinematic equations for four distinct multibody mobile robot systems: a convoy driven by 1) a unicycle, 2) a two-driving wheels vehicle, 3) a real car and 4) the first two bodies. He shows that these four control systems correspond to the same differential model, which is then used to give the same proof of controllability. Previous work proved the controllability of two-body systems and three-body systems. The main result of this paper is prove the controllability for a general n-body system View full abstract»

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  • Ultrasonic transducers with Bessel function distribution of vibrational amplitude on their surfaces

    Page(s): 732 - 739
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    In this paper the far field and near field of an ultrasonic circular transducer with a Bessel distribution of vibrational amplitude on its surface are calculated. The practical realizations of approximate Bessel-like amplitude distribution on the transducer surface are known. In this paper the vibrational characteristics of ultrasonic transducers consisting of a ceramic ring filled with a plastic disk were considered. Assuming that the amplitude on the surface of the plastic disk inside the ring is described by the Bessel function of zero order, the directivity characteristics of those transducers measured experimentally were presented. In the near zone the width of the measured main lobe is narrow, which is in accordance with the theoretical results for circular transducers with truncated Bessel function amplitude distribution. Changing the inner diameter of the ring, it is possible to control the resonance frequency of the filling plastic material. On the other hand, the resonance frequency of the ring may be regulated by varying its width, The existing coupling of resonant vibrations of the ceramic ring and plastic material enables variations of the bandwidth of the considered circular transducers. The Bessel transducers generate nondiffracting beams with a large depth of field. This is why the potential applications of Bessel transducers in robotics for object identification are worth noting View full abstract»

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  • Direct kinematics of parallel manipulators

    Page(s): 842 - 846
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    The determination of the direct kinematics of fully parallel manipulators is in general a difficult problem but has to be solved for any practical use. Various methods are presented to solve this problem: two kinds of iterative schemes, a reduced iterative scheme, and a polynomial method. The computation time of these methods are compared and their various advantages are shown View full abstract»

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  • Knowledge-based control of grasping in robot hands using heuristics from human motor skills

    Page(s): 709 - 722
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    The development of a grasp planner for multifingered robot hands is described. The planner is knowledge-based, selecting grasp postures by reasoning from symbolic information on target object geometry and the nature of the task. The ability of the planner to utilize task information is based on an attempt to mimic human grasping behavior. Several task attributes and a set of heuristics derived from observation of human motor skills are included in the system. The paper gives several examples of the reasoning of the system in selecting the appropriate grasp mode for spherical and cylindrical objects for different tasks View full abstract»

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  • Real-time vision-based robot localization

    Page(s): 785 - 800
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    This paper describes an algorithm for determining robot location from visual landmarks. This algorithm determines both the correspondence between observed landmarks (in this case vertical edges in the environment) and a stored map, and computes the location of the robot using those correspondences. The primary advantages of this algorithm are its use of a single geometric tolerance to describe observation error, its ability to recognize ambiguous sets of correspondences, its ability to compute bounds on the error in localization, and fast execution. The algorithm has been implemented and tested on a mobile robot system. In several hundred trials it has never failed, and computes location accurate to within a centimeter in less than 0.5 s View full abstract»

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  • Optimal design of robot accuracy compensators

    Page(s): 854 - 857
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    The problem of optimal design of robot accuracy compensators is addressed. Robot accuracy compensation requires that actual kinematic parameters of a robot be previously identified. Additive corrections of joint commands, including those at singular configurations, can be computed without solving the inverse kinematics problem for the actual robot. This is done by either the damped least-squares (DLS) algorithm or the linear quadratic regulator (LQR) algorithm, which is a recursive version of the DLS algorithm. The weight matrix in the performance index can be selected to achieve specific objectives, such as emphasizing end-effector's positioning accuracy over orientation accuracy or vice versa, or taking into account proximity to robot joint travel limits and singularity zones. The paper also compares the LQR and the DLS algorithms in terms of computational complexity, storage requirement, and programming convenience. Simulation results are provided to show the effectiveness of the algorithms View full abstract»

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  • Exponential control law for a mobile robot: extension to path following

    Page(s): 837 - 842
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    A piecewise smooth feedback control law for path following for the kinematic model of a nonholonomic mobile robot is proposed. The resulting motion can consist of stopping and reversing phases. The desired path is supposed to be composed of straight lines and arcs of circles joined at intermediate configurations. The proposed feedback control law yields exponential convergence to configurations representing stopping phases and to the terminal configuration View full abstract»

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  • Compliant motion control of kinematically redundant manipulators

    Page(s): 831 - 836
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    Two control schemes, termed extended hybrid control and extended impedance control, respectively, are proposed for compliant motion control of redundant manipulators. In the two control schemes, the basic compliant motion task is accomplished while the redundancy is utilized to realize some additional constraints that optimize any user-defined objective function. Some experimental results on a three-DOF planar redundant manipulator are presented to illustrate the two proposed schemes and demonstrate their capabilities for optimizing various objective functions 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