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Robotics and Automation, IEEE Journal of

Issue 6 • Date December 1987

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Displaying Results 1 - 20 of 20
  • [Front cover and table of contents]

    Publication Year: 1987 , Page(s): c1
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    Freely Available from IEEE
  • Interprocess communication for distributed robotics

    Publication Year: 1987 , Page(s): 493 - 504
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1727 KB)  

    Robot tasks have come to demand flexible sensory-based "intelligent" behavior. The single robot has given way to multiple robots cooperating in three-dimensional dynamic environments which allow them to accomplish complex and intricate tasks. Because of the complex nature of the tasks performed, centralized control is no longer practical; workcells have become centers of distributed computing. This motivates the need for an interprocess communication (IPC) facility which would integrate the individual elements both within and between workcells. A survey of IPC is presented in the context of distributed robotics. To make the survey more meaningful, it is introduced by some remarks about general approaches to communication within a distributed computing environment. A discussion of the main IPC design issues for distributed robotics is included. View full abstract»

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  • Position verification of a mobile robot using standard pattern

    Publication Year: 1987 , Page(s): 505 - 516
    Cited by:  Papers (53)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1170 KB)  

    As mobile robots are taking on more and more of the tasks that were normally delegated to humans, they need to acquire higher degrees of autonomous operation, which calls for accurate and efficient position determination and/or verification. The critical geometric dimensions of a standard pattern are used here to locate the relative position of the mobile robot with respect to the pattern; by doing so, the method does not depend on values of any intrinsic camera parameters, except the focal length. In addition, this method has the advantages of simplicity and flexibility. This standard pattern is also provided with a unique identification code, using bar codes, that enables the system to find the absolute location of the pattern. These bar codes also assist in the scanning algorithms to locate the pattern in the environment. A thorough error analysis and experimental results obtained through software simulation are presented, as well as the current direction of our work. View full abstract»

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  • Minimum operations and minimum parameters of the dynamic models of tree structure robots

    Publication Year: 1987 , Page(s): 517 - 526
    Cited by:  Papers (44)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (865 KB)  

    An efficient method for the calculation of the inverse dynamic models of tree structure robots is presented. The given method reduces significantly the computational burden such that the inverse dynamics can be computed in real time at servo rate. The method leads almost directly to models with a minimum number of arithmetic operations. The method is based on a Newton-Euler formulation that is linear in the inertial parameters, on an iterative symbolic procedure, and on condensating the inertial parameters by regrouping and eliminating some of them. The description of the robot is carried out by a new notation inspired from Denavit and Hartenberg notation. A Fortran program has been developed to generate automatically the dynamic models of tree structure robots. View full abstract»

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  • Segmented descriptions of 3-D surfaces

    Publication Year: 1987 , Page(s): 527 - 538
    Cited by:  Papers (57)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1624 KB)  

    A method to segment and describe visible surfaces of three-dimensional (3-D) objects is presented by first segmenting the surfaces into simple surface patches and then using these patches and their boundaries to describe the 3-D surfaces. First, distinguished points are extracted which will comprise the edges of segmented surface patches, using the zero-crossings and extrema of curvature along a given direction. Two different methods are used: if the sensor provides relatively noise-free range images, the principal curvatures are computed at only one resolution, otherwise, a multiple scale approach is used and curvature is computed in four directions 45° apart to facilitate interscale tracking. These points are then grouped into curves and these curves are classified into different classes which correspond to significant physical properties such as jump boundaries, folds, and ridge lines (or smooth extrema). Then jump boundaries and folds are used to segment the surfaces into surface patches, and a simple surface is fitted to each patch to reconstruct the original objects. These descriptions not only make explicit most of the salient properties present in the original input, but are more suited to further processing, such as matching with a given model. The generality and robustness of this approach is illustrated on scene images with different available range sensors. View full abstract»

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  • Positioning error analysis for robot manipulators with all rotary joints

    Publication Year: 1987 , Page(s): 539 - 545
    Cited by:  Papers (8)
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    Advanced industrial robots are commanded to accomplish different tasks with program sequences that are executed in digital computers. The operating software within these computers provides users with information on positions and orientations of the end effectors by computing them as functions of the joint variables. These functions are generally not exact enough such that differences between the computed and the actual positions can be significant. Error sources that contribute to these differences for robots with rotary joints are examined. The effects of these errors are parameterized and measurement data are fitted to obtain the values of these parameters. It is concluded that with sufficient but not exhaustive detail in the error modeling the differences can be reduced significantly from 5.9-mm mean error with nominal model down to 0.28-mm mean error after error compensation. View full abstract»

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  • Force interaction and allocation for the legs of a walking vehicle

    Publication Year: 1987 , Page(s): 546 - 555
    Cited by:  Papers (28)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1003 KB)  

    Force is often used in the control of the legs of a walking machine to allow a vehicle to adapt to terrain irregularity. However, interactions in force among the legs have the capability of causing control system instabilities if not properly treated. Different criteria for allocating forces to the legs of a walking machine are considered, properties of force-induced instability modes are studied, and the plan of hybrid control allocated by legs as a means of avoiding these force interaction modes without requiring an excessively high control frequency is introduced. View full abstract»

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  • Pipelined computation of manipulator modeling matrices

    Publication Year: 1987 , Page(s): 556 - 566
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1221 KB)  

    It is essential for the robust control of a dynamic system to employ a characterization of its inertia content in the control formulation. One such characterization is described for the nonlinear time-varying system of a robotic manipulator in the form of pipelined modeling software which is implemented on a medium-sized array processor to run in real time. The time-varying inertia content of the manipulator is expressed in terms of kinematic influence coefficients which are represented by explicit functions of only the generalized coordinates. Properties of these influence coefficients are employed to reduce the computation effort necessary to generate the modeling coefficients. To efficiently pipeline this algorithm, the structure inherent in the problem is exploited to allow extensive use of data-dependent addressing which is employed to compute multiple "small" operations within a single pipeline. The resulting software consists of two portions-- an off-line portion generates integer offset vectors to direct the addressing of the on-line portion in computing the modeling coefficients. The real-time algorithm is fourth-order in the number of links requiring 7.5 ms on a modest-sized array processor to compute the modeling coefficients of a general six-link manipulator. View full abstract»

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  • Normal forms of stiffness and compliance matrices

    Publication Year: 1987 , Page(s): 567 - 572
    Cited by:  Papers (22)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    A generalized spring associates potential energy with each position and orientation of a rigid body. The stiffness of such a spring can be represented by a 6 × 6 symmetric matrix. This matrix can be brought to a normal form by a particular choice of the coordinate frame. Analogous but independent results hold for compliance matrices. These results, obtained by using a Lie group approach, also extend the concept of the remote center of stiffness to generic generalized springs. View full abstract»

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  • MOGRER: A vehicle study and realization for in-pipe inspection tasks

    Publication Year: 1987 , Page(s): 573 - 582
    Cited by:  Papers (24)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1203 KB)  

    A three-wheeled vehicle for in-pipe monitoring tasks is described. The vehicle is basically composed of two hinged arms building what is hereafter referenced as a scissor structure. The arms are joined at one end. Another joint connects the middle points of the lower parts, called links. A wheel located at the pivot of the scissor structure is driven by an electric dc motor. Two other wheels located at the ends of the links (sphere bearings) are not actuated and can roll freely in any direction. Since the force of the arm mechanism pushing against the pipe wall is generated mechanically by an extension spring combined with levers, the vehicle rests in the pipe by pressing its wheels in the direction of maximum pipe cross section. The vehicle moves automatically by action of the driving wheel in the direction in which the pipe extends. The relation between the stretch force and the configuration of the vehicle is analyzed to optimize the lengths of the levers and the direction in which the levers should be attached for force generation. The geometric and kinematic conditions of the vehicle are investigated to make it move stably. Results of a simulation of locomotion proved the capability of self-adjustment of the vehicle to different pipe shapes and sizes. The resulting vehicle mechanism, called MOGRER, was built to carry a CCD video camera attached to its body for in-pipe monitoring tasks. Experimental results show that MOGRER can monitor while moving in an inclined pipe with a heavy angle, overcoming the effects of gravity and changes in pipe size and shape. View full abstract»

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  • Analysis of discrete dynamic robot models

    Publication Year: 1987 , Page(s): 583 - 590
    Cited by:  Papers (1)
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    The discrete shift-transformation matrix of general orthogonal polynomials is introduced. The discrete shift-transformation matrix is employed to transform the difference equations, which describe the discrete dynamic robot model, into algebraic equations. Several lemmas are introduced which, together with the discrete shift-transformation matrix, solve for the joint positions and velocities of discrete dynamic robot models via discrete orthogonal polynomials approximations. The initial numerical experiment with a cylindrical coordinate robot shows the feasibility and applicability of discrete orthogonal polynomials approximations. View full abstract»

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  • On-line compensation of mobile robot docking errors

    Publication Year: 1987 , Page(s): 591 - 598
    Cited by:  Papers (12)
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    One of the main problems of an unconstrained mobile robot (that is not limited to rails or tracks), that limits its industrial applications, is its docking accuracy. Because robot programs are executed relative to the robot base, inaccurate positioning of the mobile robot during docking must be accounted for in order to improve the accuracy of the mobile robot. In this paper, a method to compensate for the docking inaccuracy of mobile robots is proposed. The method is based on modifying the task of the robot arm according to the docking error-the offset between the desired and actual docking locations of the mobile robot. The docking error is sensed by a sensor mounted on the robot arm: it can be either a vision system or a touch trigger probe. The algorithms for calculating the spatial docking error for each sensor and how the robot's task is modified accordingly are presented. The need for a method that will allow to reach results even in the presence of perturbed data, something that currently applied methods cannot guarantee, is discussed and one is presented. The calculation of the spatial offset between the actual and the desired locations of the mobile robot using vision system was implemented and results of some experiments are presented and discussed. View full abstract»

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  • Determining object motion in a sequence of stereo images

    Publication Year: 1987 , Page(s): 599 - 614
    Cited by:  Papers (20)  |  Patents (2)
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    The motion of a three-dimensional object is determined from a sequence of stereo images by extracting three-dimensional features, establishing correspondences between these features, and finally, computing the rigid motion parameters. Three-dimensional features are extracted from the depth map of a scene. A two-pass relaxation method is developed for matching features extracted from successive depth maps. In each iteration, geometrical relationships between a feature and its neighbors in one map are compared to those between a candidate in the other map and its neighbors to update the matching probability of the candidate. The comparison of the geometrical relationship is based on the principle of conservation of distance and angle between features during rigid motion. The use of three-dimensional features allows one to find the rotation and translation components of motion separately via solving linear equations. Experimental results using several sets of real data are presented to illustrate results and difficulties. View full abstract»

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  • Dual-number transformation and its applications to robotics

    Publication Year: 1987 , Page(s): 615 - 623
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (905 KB)  

    In robotics, to deal with coordinate transformation in three-dimensional (3D) Cartesian space, the homogeneous transformation is usually applied. It is defined in the four-dimensional space, and its matrix multiplication performs the simultaneous rotation and translation. The homogeneous transformation, however, is a point transformation. In contrast, a line transformation can also naturally be defined in 3D Cartesian space, in which the transformed element is a line in 3D space instead of a point. In robotic kinematics and dynamics, the velocity and acceleration vectors are often the direct targets of analysis. The line transformation will have advantages over the ordinary point transformation, since the combination of the linear and angular quantities can be represented by lines in 3D space. Since a line in 3D space is determined by four independent parameters, finding an appropriate type of "number representation" which combines two real variables is the first key prerequisite. The dual number is chosen for the line representation, and lemmas and theorems indicating relavent properties of the dual number, dual vector, and dual matrix are proposed. This is followed by the transformation and manipulation for the robotic applications. The presented procedure offers an algorithm which deals with the symbolic analysis for both rotation and translation. In particular, it can effectively be used for direct determination of Jacobian matrices and their derivatives. It is shown that the proposed procedure contributes a simplified approach to the formulation of the robotic kinematics, dynamics, and control system modeling. View full abstract»

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  • Kalman filtering, smoothing, and recursive robot arm forward and inverse dynamics

    Publication Year: 1987 , Page(s): 624 - 639
    Cited by:  Papers (37)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1794 KB)  

    The inverse and forward dynamics problems for multilink serial manipulators are solved by using recursive techniques from linear filtering and smoothing theory. The pivotal step is to cast the system dynamics and kinematics as a two-point boundary-value problem. Solution of this problem leads to filtering and smoothing techniques similar to the equations of Kalman filtering and Bryson-Frazier fixed time-interval smoothing. The solutions prescribe an inward filtering recursion to compute a sequence of constraint moments and forces followed by an outward recursion to determine a corresponding sequence of angular and linear accelerations. An inward recursion refers to a sequential technique that starts at the tip of the terminal link and proceeds inwardly through all of the links until it reaches the base. Similarly, an outward recursion starts at the base and propagates out toward the tip. The recursive solutions are O(N), in the sense that the number of required computations only grows linearly with the number of links. A technique is provided to compute the relative angular accelerations at all of the joints from the applied external joint moments (and vice versa). It also provides an approach to evaluate recursively the composite multilink system inertia matrix and its inverse. The main contribution is to establish the equivalence between the filtering and smoothing techniques arising in state estimation theory and the methods of recursive robot dynamics. The filtering and smoothing architecture is very easy to understand and implement. This provides for a better understanding of robot dynamics. While the focus is not on exploring computational efficiency, some initial results in that direction are obtained. This is done by comparing performance with other recursive methods for a planar chain example. The analytical foundation is laid for the potential use of filtering and smoothing techniques in robot dynamics and control. View full abstract»

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  • Simplified generation of all mechanical assembly sequences

    Publication Year: 1987 , Page(s): 640 - 658
    Cited by:  Papers (117)  |  Patents (1)
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    Bourjault has presented a method which will generate all valid assembly sequences for the set of parts that constitute an assembly. A modification of Bourjault's method is presented which makes practical the application of this technique of assembly analysis to assemblies with greatly increased part count. The salient difference between the two methods is in the form and number of the questions whose answers yield the relations that allow algorithmic generation of assembly sequences. Bourjault's method requires 2l^{2} questions plus an often-large number of subsequent questions whose existence depends on answers to part of the former question set; all have yes or no answers. (Here l is the number of relations between parts.) The modified method requires 2l questions that are answered in a precedence-logical form; the questions are similar to those asked by an engineer contemplating assembly of a set of parts. Applications and techniques for use are presented, and examples are shown for l as great as 18. View full abstract»

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  • Task assignment and load balancing of autonomous vehicles in a flexible manufacturing system

    Publication Year: 1987 , Page(s): 659 - 671
    Cited by:  Papers (11)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1390 KB)  

    A graph-theoretic approach for determining an optimal task (or routing) assignment of p autonomous vehicles (AV's) among m workstations in a flexible manufacturing system which both minimizes the assignment completion time and balances the load among the AV's is presented. This task assignment problem is equivalent to an optimal routing assignmenl of destinating the m workstations to the p autonomous vehicles. A cost function is defined in terms of the job execution time and the traveling time performed by the AV's. Optimization of the objective function is based on the minimax of the job execution time and the minimization of max-min of the traveling time. This optimal task assignment problem is known to be NP-complete. Thus the problem is solved by a state-space search method-the A algorithm. The A algorithm is a classical minimum-cost graph search method. It is guaranteed to find an optimal solution if the evaluation function which utilizes the heuristic information about the problem for speeding up the search is properly defined. If potential collisions exist on the optimal routing assignment, then dynamic collision detection must be carried out during the state-space search to guarantee an optimal collision-free routing assignment. This collision avoidance can be taken care of by using an ordered collision matrix to adjust the arrival time of every AV arriving at the center of the "collision zone" if a potential collision is detected. Again, the A search strategy can be utilized to obtain an optimal collision-free routing assignment, and the optimal assignment obtained also achieves load balancing of the p AV's. View full abstract»

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  • Robot navigation in unknown terrains using learned visibility graphs. Part I: The disjoint convex obstacle case

    Publication Year: 1987 , Page(s): 672 - 681
    Cited by:  Papers (44)
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    The problem of navigating an autonomous mobile robot through unexplored terrain of obstacles is discussed. The case when the obstacles are "known" has been extensively studied in literature. Completely unexplored obstacle terrain is considered. In this case, the process of navigation involves both learning the information about the obstacle terrain and path planning. An algorithm is presented to navigate a robot in an unexplored terrain that is arbitrarily populated with disjoint convex polygonal obstacles in the plane. The navigation process is constituted by a number of traversals; each traversal is from an arbitrary source point to an arbitrary destination point. The proposed algorithm is proven to yield a convergent solution to each path of traversal. Initially, the terrain is explored using a rather primitive sensor, and the paths of traversal made may be suboptimal. The visibility graph that models the obstacle terrain is incrementally constructed by integrating the information about the paths traversed so far. At any stage of learning, the partially learned terrain model is represented as a learned visibility graph, and it is updated after each traversal. It is proven that the learned visibility graph converges to the visibility graph with probability one when the source and destination points are chosen randomly. Ultimately, the availability of the complete visibility graph enables the robot to plan globally optimal paths and also obviates the further usage of sensors. View full abstract»

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  • Adaptive friction compensation in dc-motor drives

    Publication Year: 1987 , Page(s): 681 - 685
    Cited by:  Papers (70)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (565 KB)  

    A control scheme is proposed where the nonlinear effects of friction are compensated adaptively. When the friction is compensated, the motor drive can approximately be described by a constant coefficient linear model. Standard methods can be applied to design a regulator for such a model. This results in a control law which is a combination of a fixed linear controller and an adaptive part which compensates for nonlinear friction effects. Experiments have clearly shown that both static and dynamic friction have nonsymmetric characteristics. They depend on the direction of motion. This is considered in the design of the adaptive friction compensation. The proposes scheme has been implemented and tested on a laboratory prototype with good results. The control law is implemented on an IBM PC. The ideas, algorithm, and experimental results are described. The results are relevant for many precision drives, such as those found in industrial robots. View full abstract»

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  • [Back cover]

    Publication Year: 1987 , Page(s): c4 - 0
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    Freely Available from IEEE

Aims & Scope

This Journal ceased production in 1988. The current retitled publications are IEEE Transactions on Automation Science and Engineering and IEEE Transactions on Robotics.

Full Aims & Scope