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Robotics and Automation, IEEE Journal of

Issue 6 • Date Dec 1988

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Displaying Results 1 - 11 of 11
  • Dynamic hybrid position/force control of robot manipulators-controller design and experiment

    Page(s): 699 - 705
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    An approach to designing controllers for dynamic hybrid position/force control of robot manipulators is presented, and preliminary experimental results are given. Dynamic hybrid control is an extension of an approach proposed by M.H. Raibert and J.J. Craig (1981) to the case where the full manipulator dynamics is taken into consideration and the end-effector constraint is explicitly given by the constraint hypersurfaces. This design method consists of two steps. The first step is the linearization of the manipulator dynamics by nonlinear state feedback. Formulation of the constraint by the constraint hypersurfaces plays an essential role in establishing the linearizing law. The second step is the design of position and force controllers for the linearized model using the concept of two-degrees-of-freedom servocontroller. The merit of this servocontroller is that it can take account of both the command response and the robustness of the controllers to modeling errors and disturbances. Preliminary experiments using a SCARA robot show the validity of the approach View full abstract»

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  • Symbolic derivation of dynamic equations of motion for robot manipulators using Piogram symbolic method

    Page(s): 599 - 609
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    An algorithm for both manual and automatic derivation of dynamic models of robotic manipulators using the Piogram symbolic method is presented. A program is also developed based on the Newton-Euler formalism by the Piogram symbolic representation method, which is applicable to manipulators of any degree of freedom. Two examples are given to illustrate how to use this program for dynamic equation generation. It is shown that the method has the advantage of simplifying the manipulation process, and thus a large amount of memory space and computing time when the method is implemented in a computer program View full abstract»

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  • Omnidirectional supervisory control of a multilegged vehicle using periodic gaits

    Page(s): 635 - 642
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    A novel algorithm is described for omnidirectional control of a multilegged robot vehicle using periodic gaits. The vehicle model is chosen from a hexapod robot vehicle, named the Adaptive Suspension Vehicle, which is under development. To implement periodic gaits for omnidirectional control, the notion of the constrained working volume (CWV) is introduced on the basis of reachability of the leg and the kinetic maximum locomotion period is defined using the CWV. As a result, the leg touchdown and liftoff points are constrained within the CWV during vehicle locomotion. Based on this constraint, the foothold selection problem is addressed. The algorithm was developed through a computer graphics simulation; results of the simulations are discussed View full abstract»

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  • Real-time control of robot manipulators in the presence of obstacles

    Page(s): 687 - 698
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    A novel approach is suggested to the problem of obstacle avoidance for a point robot moving among circular or elliptical/spherical or ellipsoid obstacles. The obstacle avoidance strategy (OAS) translates each state constraint (obstacle) into a state-dependent control constraint (SDCC). Each SDCC defines a hyperplane in the control space u. The intersection of the SDCC sets with the hard control bounds forms a polygon in u. The optimal decision strategy (ODS) control algorithm is then used to find the control which lies in this polygon-assuring obstacle avoidance-and minimizes the deviation between the acceleration vector of the point robot and a desired acceleration field. Simulation results display the effectiveness of the algorithm for a workspace hosting multiple obstacles. The OAS algorithm has been implemented successfully on a small Cartesian-coordinate robot View full abstract»

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  • A group-theoretic approach to the computation of symbolic part relations

    Page(s): 622 - 634
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    When a set of constraints is imposed on the degrees of freedom between several rigid bodies, finding the configuration or configurations that satisfy all these constraints is a matter of special interest. The problem is not new and has been discussed, not only in kinematics, but also more recently in the design of object-level robot programming languages. In this last domain, several languages have been developed, from different points of view, that are able to partially solve the problem. A more general method is derived than those previously proposed that were based on the symbolic manipulation of chains of matrix products, using the theory of continuous groups View full abstract»

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  • Robot calibration and compensation

    Page(s): 643 - 656
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    A method is presented for calibrating and compensating for the kinematic errors in robot manipulators. A method of selecting a set of independent kinematic errors for modeling any geometric errors in a manipulator's structure is developed. A calibration algorithm is presented for finding the values of these kinematic errors by measuring the end-effector position. These kinematic errors are experimentally determined for a PUMA 560 six-joint manipulator. Two general-purpose compensation algorithms are developed and the improvement in the Cartesian position of the end-effector is experimentally measured and these results are presented. The results show that the positioning accuracy of a robot manipulator can be substantially improved using a relatively simple technique for measuring the Cartesian position of a tool attached to the end of the manipulator View full abstract»

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  • The motion of a pushed, sliding workpiece

    Page(s): 569 - 598
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    It occurs frequently in robotic applications that a robot manipulates a workpiece which is free to slide on a work surface. Because the pressure distribution supporting the workpiece on the work surface cannot in general be known, the motion of the workpiece cannot be calculated uniquely. The authors find the locus of centers of rotation of a workpiece for all possible pressure distributions. The results allow a quantitative understanding of open-loop robot motions which guarantee the alignment of a workpiece. Several sample problems are solved using the results, including the distance that a flat fence, or robot finger, must push a polygonal workpiece to assure that a facet of the workpiece comes into alignment with the fence View full abstract»

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  • Force distribution in closed kinematic chains

    Page(s): 657 - 664
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    The problem of force distribution in systems involving multiple frictional contacts between actively coordinated mechanisms and passive objects is examined. The special case in which the contact interaction can be modeled by three components of forces (zero moments) is particularly interesting. The Moore-Penrose generalized inverse solution for such a model (point contact) is shown to yield a solution vector such that the difference between the forces at any two contact points projected along the line joining the two points vanishes. Such a system of contact forces is described by a helicoidal vector field which is geometrically similar to the velocity field in a rigid body twisting about an instantaneous screw axis. A method to determine this force system is presented. The possibility of superposing another force field which constitutes the null system is also investigated View full abstract»

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  • Fixed-axis tool positioning with built-in global interference checking for NC path generation

    Page(s): 610 - 621
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    An algorithm for generating tool positions for three-axis mill cutter paths on parametric surfaces is presented. The novelty of this algorithm is in its use of a surface subdivision technique as an alternative to the traditional APT-style iterative approaches based on local tangent-plane extensions. The algorithm presented provides global interference checking and does not exhibit the convergence problems of the traditional approaches View full abstract»

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  • On the stability of manipulators performing contact tasks

    Page(s): 677 - 686
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    Manipulation requires contact with the object being manipulated, and the full potential of robots can only be realized when they are applied to contact tasks. One of the difficulties engendered by contact tasks is that they require intimate dynamic interaction between the robot and its environment. That interaction changes the performance of the robot and can jeopardize the stability of its control system. A discussion is presented of the problem of preserving the stability of a manipulator's control system during contact tasks. It will be shown that contact stability may be guaranteed if the control system provides the manipulator with an appropriately structured dynamic response to environmental inputs. Two aspects of one implementation of such a controller will be considered. Robustness to large errors in the manipulator kinematic equations and to unmodeled interface dynamics is shown View full abstract»

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  • Efficient modeling and computation of manipulator dynamics using orthogonal Cartesian tensors

    Page(s): 665 - 676
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    The authors use orthogonal second-order Cartesian tensors to formulate the Newton-Euler dynamic equations for a robot manipulator. Based on this formulation, they develop two efficient recursive algorithms for computing the joint actuator torques/forces. The proposed algorithms are applicable to all rigid-link manipulators with open-chain kinematic structures with revolute and/or prismatic joints. An efficient implementation of one of the proposed algorithms shows that the joint torques/forces for a six-degrees-of-freedom manipulator with revolute joints, can be computed in approximately 489 multiplications and 420 additions. For manipulators with zero or 90° twist angles, the required computations are reduced to 388 multiplications and 370 additions. For manipulators with even simpler geometric structures, these arithmetic operations can be further reduced to 277 multiplications and 255 additions View full abstract»

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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