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Robotics and Automation, IEEE Transactions on

Issue 1 • Date Feb 2000

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Displaying Results 1 - 12 of 12
  • A learning controller for robot manipulators using Fourier series

    Page(s): 36 - 45
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    We proposed a new learning controller for decentralized tracking control of nonlinear robot manipulators. When the desired trajectory of each subsystem of the robot lasts for a finite duration, it can be approximated by a Fourier series with constant harmonic magnitudes. For each subsystem of the robot, a learning controller is designed to individually control each harmonic component of the actual output, although it is cross-related to other components in nonlinear systems. The learning algorithm is designed such that each harmonic magnitude of the actual output converges to that of the desired trajectory within the system bandwidth. Since this decentralized learning controller is designed in Fourier space instead of time domain, the system's time-delay could be easily compensated. This learning controller is only based on the local input and output information; no a priori structure or parameters of the system model are required. The experimental results on a 3-DOF direct-drive robot are presented View full abstract»

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  • Rigid body analysis of the indeterminate grasp force in power grasps

    Page(s): 46 - 54
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    This paper analyzes the indeterminate grasp force in power grasps with a rigid body model. A power grasp overconstrains an object with multiple contact points using the surfaces of finger links and palm. It is known that the overconstrained grasp results in the static indeterminacy of the grasp force. This paper shows that it also results in an infeasible combination of the sliding directions at the contact points. A static friction force acts only in the opposite direction of the trend of sliding. This characteristic of friction restricts the grasp force in power grasps although it is indeterminate. We first show an example to illustrate the restriction on the grasp force, and then formulate it formally. This analysis leads to a special case where the grasp force is unique View full abstract»

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  • Adaptive output regulation of robot manipulators under actuator constraints

    Page(s): 29 - 35
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    This paper considers the global regulation of robot manipulators without velocity measurement and proposes an adaptive controller for the case where the gravity torque presents an uncertainty. The proposed adaptive controller ensures both the semi-global convergence and the convergence of the position error to zero under actuator constraints View full abstract»

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  • The bounds and realization of spatial compliances achieved with simple serial elastic mechanisms

    Page(s): 99 - 103
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (108 KB)  

    We address the spatial elastic behavior that can be achieved through the use of a serial chain of revolute and prismatic elastic joints. We show that, regardless of the number of joints or the configuration of the links, there exists a subspace within the 21-dimensional compliance matrix space that cannot be reached by a simple serial elastic mechanism. This restriction is shown to be dual to the restriction on the stiffness matrices associated with simple parallel mechanisms. Although analogous to each other, the two restrictions correspond to different elastic behaviors. A procedure to synthesize any realizable compliance matrix with a simple serial mechanism is provided. The dualities and differences between the parallel and serial cases are discussed View full abstract»

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  • Modeling and supervisory control of a disassembly automation workcell based on blocking topology

    Page(s): 67 - 77
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    This paper describes a model for automated disassembly that accounts for workcell interaction and used product constraints. The model provides an essential means to determine, in real-time, the next component for disassembly using the knowledge of the product design and sensor feedback minimizing the steps to remove goal components. Sets of components for removal were resolved by minimizing setup time for disassembling the component. Given the model, a controller for product disassembly is defined that can account for missing and known replacement components. The controller can recover from unknown replacement components and jammed components when alternate removal sequences exist to meet the cell goal. Two case study examples are presented and experimentally simulated. Simulation results based on real product, vision sensor measure, and process input are presented and discussed. It is expected that the concepts demonstrated through these case studies can provide useful insights into other mechanical assemblies View full abstract»

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  • Kinematic analysis and design of surface wave distributed actuators with application to a powered bed for bedridden patients

    Page(s): 1 - 11
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    A surface wave distributed actuation method and its potential for transporting bedridden patients is explored. First, the basic principle of surface wave distributed actuation is presented, followed by kinematic modeling and analysis. Based on the analysis, modifications to natural wave transport are made to enhance transport efficiency and human comfort. Further kinematic analysis reveals that an object can be transferred by a simplified actuator architecture that makes the concept amenable to hardware realization. Two proof-of-concept prototypes are designed, built, and tested. The first is a powered water bed consisting of a water vat, a flexible mat placed on the water surface, and an exciter creating surface waves at resonant frequencies. The other is a powered mechanical bed having an array of coordinated active nodes that generate psuedo-continuum surface waves. Experiments demonstrate the surface wave actuation concept and verify the analytical results View full abstract»

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  • The direct kinematics of parallel manipulators under joint-sensor redundancy

    Page(s): 12 - 19
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    We study, for each of the possible joint-sensor layouts, the subspaces into which the motion of the hip-attachment points of parallel manipulators are completely measured. The projection of the motion of these points onto their subspaces allows us to write the underlying direct kinematics as a linear algebraic system constrained by the proper orthogonality of the rotation matrix. Although the solution of this problem requires a nonlinear technique, we propose a linear procedure that provides what we term a polar least square estimate. The resulting procedure is fast, robust to measurement noise, and produces estimates with about the same accuracy as a nonlinear procedure View full abstract»

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  • Probabilistic self-localization for mobile robots

    Page(s): 55 - 66
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    We describe probabilistic self-localization techniques for mobile robots that are based on the principle of maximum-likelihood estimation. The basic method is to compare a map generated at the current robot position with a previously generated map of the environment in order to probabilistically maximize the agreement between the maps. This method is able to operate in both indoor and outdoor environments using either discrete features or an occupancy grid to represent the world map. The map may be generated using any method to detect features in the robot's surroundings, including vision, sonar, and laser range-finder. We perform an efficient global search of the pose space that guarantees that the best position is found according to the probabilistic map agreement measure in a discretized pose space. In addition, subpixel localization and uncertainty estimation are performed by fitting the likelihood function with a parameterized surface. We describe the application of these techniques in several experiments View full abstract»

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  • Measuring and reducing the Euclidean-space effects of robotic joint failures

    Page(s): 20 - 28
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    Robotic joint failures are directly characterized and measured in joint space. A locking failure, for example, is one for which a joint cannot move, and it gives an error equal to the desired value minus the locked value. This article extends the joint-space characterization to Euclidean space by measuring the failure effect. The approach is based on a rudimentary measure of point error that can be defined to be distance or path length. It is used to form comprehensive measures through weighted integration over Euclidean-space regions. For kinematically redundant manipulators, minimizing the measures using the redundancy is a method to induce failure tolerance. This can be applied both before a failure to reduce the likelihood of collision-induced damage and after a failure to reduce end-effector error. Examples for both cases are given View full abstract»

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  • Dynamics analysis of the Gough-Stewart platform manipulator

    Page(s): 94 - 98
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    A novel derivation of the forward dynamic equations for the Gough-Stewart platform manipulator based on Kane's equation is proposed. In this method, each leg of the Gough-Stewart platform manipulator is treated as an independent substructure, the system dynamic equations are composed of the equations of legs and platform according to the constraints among substructures. The formulation has been implemented in MATLAB routines, and simulation results have been given to show the validation of the new approach. Compared with the traditional Newton-Euler method and Lagrange formulation, the modeling process proposed in the paper is more straightforward and systematic, and the final dynamic equations are very concise View full abstract»

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  • Time-optimal controls of kinematically redundant manipulators with geometric constraints

    Page(s): 89 - 93
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    Theoretical investigations of time-optimal control of kinematically redundant manipulators subject to control and state constraints are presented. The task is to move the end-effector along a prescribed geometric path (state equality constraints). In order to address a structure of time-optimal control, the concept of a regular trajectory derived in Pontryagin et al. (1961) and the extended state space introduced herein are used. Next, it is proved that if the dynamics of a manipulator are defined by n actuators and m path-constrained equations, where m<n, then at most n-m+1 actuators are saturated, provided that the time-optimal manipulator trajectory is regular with respect to a prescribed geometric path given in the work space. Besides, it is shown that these results are also consistent for a point-to-point time-optimal control problem. A computer example involving a planar redundant manipulator of three revolute kinematic pairs is included which confirms the obtained theoretical results View full abstract»

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  • Lagrangian relaxation neural networks for job shop scheduling

    Page(s): 78 - 88
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    Manufacturing scheduling is an important but difficult task. In order to effectively solve such combinatorial optimization problems, the paper presents a Lagrangian relaxation neural network (LRNN) for separable optimization problems by combining recurrent neural network optimization ideas with Lagrangian relaxation (LR) for constraint handling. The convergence of the network is proved, and a general framework for neural implementation is established, allowing creative variations. When applying the network to job shop scheduling, the separability of problem formulation is fully exploited, and a new neuron-based dynamic programming is developed making innovative use of the subproblem structure. Testing results obtained by software simulation demonstrate that the method is able to provide near-optimal solutions for practical job shop scheduling problems, and the results are superior to what have been reported in the neural network scheduling literature. In fact, the digital implementation of LRNN for job shop scheduling is similar to the traditional LR approaches. The method, however, has the potential to be implemented in hardware with much improved quality and speed 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