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Robotics and Automation, IEEE Transactions on

Issue 3 • Date Jun 1991

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Displaying Results 1 - 18 of 18
  • Learning impedance parameters for robot control using an associative search network

    Page(s): 382 - 390
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (860 KB)  

    An evaluation of the associative search network (ASN) learning scheme when used for learning control parameters for robot motion is presented. The control method used is impedance control in which the controlled variables are the dynamic relations between the motion variables of the robot manipulator's tip and the forces exerted by the tip. The main task used is that of wiping a surface whose geometry is not precisely known. The learning scheme does not use a model of the robot and its environment. It is a stochastic scheme that uses a single scalar value as a measure of the system performance. The scheme is found to perform quite well. A few variants of the main scheme are discussed. Modifying the virtual trajectory, externally to the ASN scheme, shows an improved performance View full abstract»

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  • A six-degree-of-freedom magnetically levitated variable compliance fine-motion wrist: design, modeling, and control

    Page(s): 320 - 332
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1244 KB)  

    A high-performance six-degree-of-freedom magnetically levitated fine-motion wrist with programmable compliance is described. Design considerations, a discussion of the major elements of the device, and issues of modeling, kinematics, dynamics, and control are presented. A prototype wrist which has been built and controlled successfully is discussed. Experimental results, including high bandwidth position control, compliant control, and the emulation of several mechanisms through software gain setting which establish the use of magnetically levitated robot wrists as an option for manipulation tasks requiring high precision and fine compliant motions, are included View full abstract»

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  • Motion planning with six degrees of freedom by multistrategic bidirectional heuristic free-space enumeration

    Page(s): 267 - 277
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    A general and efficient method is presented that uses a configuration space for planning a collision-free path among known stationary obstacles for an arbitrarily moving object with six degrees of freedom. The basic approach is to restrict the free space concerning path planning and to avoid executing unnecessary collision detections. The six-dimensional configuration space is equally quantized into cells by placing a regular grid, and the cells concerning path planning are enumerated by simultaneously executing multiple search strategies. Search strategies of different characteristics are defined by assigning different values to the coefficients of heuristic functions. The efficiency of each search strategy is evaluated during free-space enumeration, and a more promising one is automatically selected and preferentially executed. The free-space cells are efficiently enumerated for an arbitrary moving object in all kinds of working environments. The implementation of this method on several examples that have different characteristics is discussed View full abstract»

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  • Hidden Markov model for dynamic obstacle avoidance of mobile robot navigation

    Page(s): 390 - 397
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    Models and control strategies for dynamic obstacle avoidance in visual guidance of mobile robots are presented. Characteristics that distinguish the visual computation and motion control requirements in dynamic environments from that in static environments are discussed. Objectives of the vision and motion planning are formulated, such as finding a collision-free trajectory that takes account of any possible motions of obstacles in the local environments. Such a trajectory should be consistent with a global goal or plan of the motion and the robot should move at as high a speed as possible, subject to its kinematic constraints. A stochastic motion-control algorithm based on a hidden Markov model is developed. Obstacle motion prediction applies a probabilistic evaluation scheme. Motion planning of the robot implements a trajectory-guided parallel-search strategy in accordance with the obstacle motion prediction models. The approach simplifies the control process of robot motion View full abstract»

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  • Generation of free gait-a graph search approach

    Page(s): 299 - 305
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    A method is presented for the generation of a free gait for the straight-line motion of a quadruped walking machine. It uses a heuristic graph search procedure based on the A* algorithm. The method essentially looks into the consequences of a move to a certain depth before actually committing to it. Deadlocks and inefficiencies are thus sensed well in advance and avoided View full abstract»

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  • Process planning: a knowledge-based and optimization perspective

    Page(s): 257 - 266
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    Process planning for a part involves preparation of a plan that outlines the processing route, operations, machine tools, and so on. The decomposition of the process-planning task into eight phases is discussed. For each phase, problems and suitable solution approaches are discussed. Most process-planning problems are solved using a knowledge-based approach or a combination of optimization and knowledge-based approaches. The knowledge-based approach solves the qualitative subproblems, and the optimization perspective tackles the quantitative aspect of the subproblems. The concepts presented are illustrated with examples View full abstract»

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  • The vector field histogram-fast obstacle avoidance for mobile robots

    Page(s): 278 - 288
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1088 KB)  

    A real-time obstacle avoidance method for mobile robots which has been developed and implemented is described. This method, named the vector field histogram (VFH), permits the detection of unknown obstacles and avoids collisions while simultaneously steering the mobile robot toward the target. The VFH method uses a two-dimensional Cartesian histogram grid as a world model. This world model is updated continuously with range data sampled by onboard range sensors. The VFH method subsequently uses a two-stage data-reduction process to compute the desired control commands for the vehicle. Experimental results from a mobile robot traversing densely cluttered obstacle courses in smooth and continuous motion and at an average speed of 0.6-0.7 m/s are shown. A comparison of the VFN method to earlier methods is given View full abstract»

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  • Mobile robot localization by tracking geometric beacons

    Page(s): 376 - 382
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    The application of the extended Kaman filter to the problem of mobile robot navigation in a known environment is presented. An algorithm for, model-based localization that relies on the concept of a geometric beacon, a naturally occurring environment feature that can be reliably observed in successive sensor measurements and can be accurately described in terms of a concise geometric parameterization, is developed. The algorithm is based on an extended Kalman filter that utilizes matches between observed geometric beacons and an a priori map of beacon locations. Two implementations of this navigation algorithm, both of which use sonar, are described. The first implementation uses a simple vehicle with point kinematics equipped with a single rotating sonar. The second implementation uses a `Robuter' mobile robot and six static sonar transducers to provide localization information while the vehicle moves at typical speeds of 30 cm/s View full abstract»

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  • Weld pool edge detection for automated control of welding

    Page(s): 397 - 343
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    A vision system that determines the edges of the weld pool in sequences of gas-tungsten-arc welding images acquired by a coaxial viewing system is described. The vision system uses a transformation that maps the edge of a weld pool into a vertical line. The weld pool edge is detected in the transform domain by using a directional filter, which retains only intensity changes of interest, and a one-dimensional edge detector. The edge of the weld pool, in the physical domain, is determined using the inverse transformation. The transformation uses parameters that are updated when processing a sequence of images, and are initially determined by analyzing the first image frame in the physical domain View full abstract»

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  • Path planning for mobile manipulators for multiple task execution

    Page(s): 403 - 408
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    The planning problem for a mobile manipulator system that must perform a sequence of tasks defined by position, orientation, force, and moment vectors at the end-effector is considered. Each task can be performed in multiple configurations due to the redundancy introduced by mobility. The planning problem is formulated as an optimization problem in which the decision variables for mobility (base position) are separated from the manipulator joint angles in the cost function. The resulting numerical problem is nonlinear with nonconvex, unconnected feasible regions in the decision space. Simulated annealing is proposed as a general solution method for obtaining near-optimal results. The problem formulation and numerical solution by simulated annealing are illustrated for a manipulator system with three degrees of freedom mounted on a base with two degrees of freedom. The results are compared with results obtained by conventional nonlinear programming techniques customized for the particular example system View full abstract»

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  • Segmentation via manipulation

    Page(s): 306 - 319
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    A paradigm of iterative, interactive scene segmentation and simplification of random heaps of unknown objects via vision and manipulation is introduced. The scene simplification is based on the graph operations of vertex and edge removal. These operations are defined isomorphic to the pick and push manipulation actions. Sensors are used as graph generators and the manipulator is used as the decomposing mechanism of the graphs. The model is a nondeterministic finite-state Turing machine. A vision system, a manipulator, and force/torque and other sensory input are integrated into a robot work cell. Experiments conducted to test convergence and error recovery of four different strategies are discussed. It is found that under certain conditions the strategies can tolerate errors in the sensory data, recover from pathological states, and converge View full abstract»

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  • Shortest path planning in discretized workspaces using dominance relation

    Page(s): 342 - 350
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    A method of partitioning a workspace using rectilinear visibility in 3-D or higher space is presented. Unlike the case of 2-D space where the shape of a partition is a rectangle, the shape of a partition in 3-D or higher space is arbitrary. The existence of dominance relations between the partitioned regions is proven. This relation is then utilized to efficiently solve the shortest path planning problem in 3-D or higher space View full abstract»

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  • Adjusting step length for rough terrain locomotion

    Page(s): 289 - 298
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    The task of controlling step length in the context of a dynamic biped robot that actively balances itself as it runs is discussed. Three methods for controlling step length, each of which adjusts a different parameter of the running cycle, are discussed. The adjusted parameters are forward running speed, running height, and duration of ground contact. All three control methods are successful in manipulating step length in laboratory experiments, but the method that adjusted forward speed provided the widest range of step lengths with accurate control of step length. The three methods for controlling step length manipulated the dynamics of the system so the feet could be placed on the available footholds without disturbing the system's balance. An alternative approach which ignores balance for a single step, placing the foot directly on the desired foothold, and recovering balance later is described View full abstract»

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  • The effect of monocular target blur on simulated telerobotic manipulation

    Page(s): 372 - 376
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    A simulation involving three types of telerobotic tasks that require information about the spatial position of objects is reported. This is similar to the results of psychophysical experiments examining the effect of blur on stereoacuity. It is suggested that other psychophysical experimental results could be used to predict operator performance for other telerobotic tasks. It is demonstrated that refractive errors in the helmet-mounted stereo display, system can affect performance in the three types of telerobotic tasks. The results of two sets of experiments indicate that monocular target blur of two diopters or more degrades stereo display performance to the level of monocular displays. This indicates that moderate levels of visual degradation that affect the operator's stereoacuity may eliminate the performance advantage of stereo displays View full abstract»

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  • Geometric uncertainties in polyhedral object recognition

    Page(s): 361 - 371
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    It is shown, by direct geometric construction, that previously published uncertainty bounds on the location of polygonal or polyhedral objects can be tightened considerably. The improvement of the bounds is a result of considering the cross-coupling between rotational and translation uncertainties in the interpretation of the sensor data. Both two-dimensional and three-dimensional uncertainty bounding are tested in simulation. The two-dimensional studies are implemented as part of a robotic system for tactile recognition. These implementations prove to be useful vehicles for exploring the computational issues involved in a detailed analysis of the geometric uncertainties present in model-based object recognition systems. Among other results it is found that rotational uncertainty is independent of the scale of the models, and translational uncertainty is highly dependent on the relative angles of the model components that are sensed View full abstract»

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  • Impedance control with adaptation for robotic manipulations

    Page(s): 408 - 415
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    Two adaptive impedance control algorithms are presented. In this treatment, it is assumed that some parameters in the manipulator dynamics may be uncertain, and the measurements from the wrist force sensor utilized are imprecise. By introducing the concept of target-impedance reference trajectory (TIRT), which characterizes a desired dynamic relation of the end-point with the environment and a refined Lyapunov approach, it is shown that the adaptation mechanisms previously suggested can be injected into N. Hogan's (1987) conventional impedance control scheme. The two resulting algorithms are compared in terms of implementation feasibility as well as computation efficiency. Simulation results are presented to illustrate the proposed algorithms View full abstract»

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  • Vision-based automatic theodolite for robot calibration

    Page(s): 351 - 360
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    An automatic partial-pose measurement system for robot calibration, called the vision-based automatic theodolite (VBAT), is described. It uses low-resolution rotation stages and resolution enhancement from a vision system to determine the line of sight to a spherical illuminated target. Automatic tracking, focusing, and centering provide the calibration system with speed, reliability, and repeatability. It is proposed that such a measurement prototype may be constructed without expensive precision machining, provided it is calibrated before use. Simulations demonstrate that such a system may be identified by precalibration of the vision parameters, followed by calibration of the rotation stage parameters. All parameters are determined from measurements using a coordinate measuring machine. The parameter identification is formulated as a nonlinear regression problem. Verification of the VBAT calibration experiment shows that the identified model can predict the target position to a root mean square miss-distance of 0.2 mm View full abstract»

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  • Scheduling job operations in an automatic assembly line

    Page(s): 333 - 341
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    The problem of scheduling job operations in an automatic assembly line used for manufacturing a small to medium volume of mixed workparts is addressed. An assembly line model is discussed. This model differs from the classical flow shop model in the following three aspects: there are no buffers at machine stations; constraints associated with the material transport system are included; and, for each batch of production, workparts are distinguished in groups, rather than individually. An optimal algorithm that requires very little computation is derived first by minimizing the total finish time for two machine assembly lines. This result is then generalized to the problem of scheduling an assembly line with m>2 machines processing single-operation jobs. In order to reduce the computational complexity of the latter problem, heuristic algorithms are proposed and shown to work quite well for all the cases considered. A heuristic solution to the problem of scheduling an assembly line with m>2 machines processing multioperation jobs is discussed 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