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Robotics and Automation, IEEE Transactions on

Issue 1 • Date Feb 1991

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Displaying Results 1 - 19 of 19
  • Probabilistic modeling of intelligent robotic systems

    Page(s): 164 - 171
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    A probabilistic approach is followed for the modeling of intelligent robotic systems composed of three interactive levels of organization, coordination, and execution of tasks. Probability and entropy functions are used as analytic measures to interpret mathematically the system functions. The modeling constraint obeys the mathematically proven principle of increasing precision with decreasing intelligence. This probabilistic approach has been tested by simulation in connection with overcoming emergency situations in a pressurized water reactor nuclear power plant View full abstract»

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  • Robot force sensor interacting with environments

    Page(s): 156 - 164
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    The authors study the impact effect on a robotic system with a force-sensing device installed between the end-effector and the end of the robot. It is shown that physical contact of a robot with environments causes abrupt changes of velocity and force to the end-effector and the force sensor, respectively. The dynamic behavior of the force sensor following the impact is studied. Theoretical analysis and experiments show that the sensor generates a low-to-high transition signal corresponding to an impact, which can be used to identify the contact. To utilize this signal, an electronic switch is designed. The signal triggers the switch, which in turn interrupts the control computer. The control computer can then stop the robot motion immediately after an impact occurs. As a result, damage to, or malfunction of, the robotic system following the impact can be avoided. Experimental results show that the proposed switching mechanism works effectively View full abstract»

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  • Manipulating and grasping forces in manipulation by multifingered robot hands

    Page(s): 67 - 77
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    A new definition of grasping and manipulating forces for multifingered robot hands is proposed. First, a short discussion of the grasping and manipulating forces for two-fingered hands with linear motion is given to explain the motivation more clearly and to give the basic idea of the new definition. Then, for three-fingered hands, based on a representation of the internal force, the grasping force is defined as an internal force that satisfies the static friction constraint. The concept of grasp mode is also introduced. The manipulating force is then defined as a fingertip force that satisfies the following three conditions: (1) it produces the specified resultant force, (2) it is not in the inverse direction of the grasping force, (3) and it is orthogonal to the grasping force component. An algorithm for decomposing a given fingertip force into manipulating and grasping forces is presented. Extensions of the result to cases of two-fingered hands with planar motion and four-fingered hands are discussed. Finally, a simple example of synthesizing fingertip force for a given manipulation task is given to illustrate the usefulness of the proposed definition View full abstract»

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  • Some tradeoffs for interfaces to piezoresistive sensor arrays

    Page(s): 171 - 175
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    The author presents a quantitative study of some of the tradeoffs between interface electronics complexity, numerical computational burden, and number of array accesses that exist in the implementation of sensing systems using piezoelectric arrays. For each level, it is shown what information can be obtained, and algorithms are given that extract the stated information from the array. For the most capable interface, tradeoffs between computation and the number of array accesses exist; algorithms that exploit these various tradeoffs are given View full abstract»

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  • An integrated computer aid for generating and evaluating assembly sequences for mechanical products

    Page(s): 78 - 94
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    An integrated computer aid that is useful for assembly-line design and for concurrent design of mechanical products is described. Recognizing that early consideration of assembly sequence is important for producibility, quality control, flexibility, and market responsiveness, the authors have built an integrated set of user-interactive computer programs that generates all feasible assembly sequences for a product and then aids the user in judging their value based on various criteria. The programs use a disassembly analysis for generating sequences and provide online visual aids during generation and evaluation. During evaluation, matters such as avoiding difficult assembly states or moves, stability, fixturing, orientation, refixturing and reorientation count, and inclusion of favorable states are considered to highlight desirable or undesirable sequences. The designer edits the set of sequences according to these criteria, leading to an informed sequence choice or to needed design refinement. The interactive programs provide a rapid means for sequence selection, encouraging their use during early design View full abstract»

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  • A comparative study on the path length performance of maze-searching and robot motion planning algorithms

    Page(s): 57 - 66
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    A number of existing maze-searching and robot motion planning algorithms are studied from the standpoint of a single performance criterion. The main motivation is to build a framework for selecting basic planning algorithms for autonomous vehicles and robot arm manipulators that operate in an environment filled with unknown obstacles of arbitrary shapes. In choosing an appropriate criterion, it is noted that besides convergence, minimizing the length of generated paths is a single major consideration in planning algorithms. In addition, since no complete information is ever available, optimal solutions are ruled out. Accordingly, the performance criterion is defined in terms of the upper bound on the length of generated paths as a function of the maze perimeter. The comparison shows that the special structure of graphs that correspond to planar environments with obstacles actually makes it possible to exceed the efficiency of general maze-searching algorithms View full abstract»

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  • Design concept development of a spherical stepper for robotic applications

    Page(s): 175 - 181
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    The design concept of a spherical stepper motor capable of three-degrees-of-freedom (DOF) motion in a single joint is presented. The ball-joint-like motor has no singularities except at the boundary of the workspace and can perform isotropic manipulation in all three directions. Due to its relatively simple ball-like structure, undesired cross-coupling and centrifugal components of wrist rotor dynamics can be effectively minimized or eliminated. The spherical stepper motor has potential in robotic applications as a three-DOF shoulder or an eyeball, as well as a wrist actuator. In particular, the systematic conceptualization of a spherical stepper is presented, and the feasibility of constructing the spherical stepper is examined. Along with the experimental data, an analytical approach based on the permeance formula was used to predict the driving forces generated by a neodymium-iron permanent magnet. The force-displacement curves provide useful information for rational spherical motor design and control View full abstract»

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  • Theory and experiments on the stability of robot compliance control

    Page(s): 95 - 104
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    The authors present a nonlinear stability analysis for constrained robotic motion, a maneuver where the manipulator contacts the environment. The external disturbances, sensor noises, parameter uncertainties, and the dynamics of the total system composed of the robot and the environment have been modeled. The control of the manipulator is divided into two components: a computed torque trajectory controller that regulates the robot position and a compliance controller that modulates contact forces. Three sufficient conditions for stability have been derived. The first condition guarantees the stability of the system of robot and finite stiff environment when no force sensor and, consequently, no force feedback is considered for the system. The second condition guarantees stability of the robot and environment when a compliance compensator (operating on the contact force) supplements the trajectory controller. The third stability criterion shows that, for a robot contacting a very stiff environment, the gain of the compliance compensator must vary in inverse proportion to the gain of the trajectory compensator View full abstract»

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  • Determination of robot locations by common object shapes

    Page(s): 149 - 156
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    A novel approach to the determination of robot locations by common object shapes is proposed. Any object that has a polygon-shaped top and a lateral surface perpendicular to the top can be used for robot locations in the approach, as long as the top shape is known in advance. In addition, the solution provided by the approach can be computed analytically. These merits make the proposed approach more practical for general applications than other approaches using specially designed marks or requiring iterative computation. From a monocular image of an object, image processing and numerical analysis techniques are applied to extract the projection characteristics of the polygon corners on the object top surface, from which the position and the orientation parameters of a camera-mounted robot can be determined. Experimental results with location errors less than 5% prove the feasibility of the proposed approach. Error analysis that is useful for choosing better viewing angles to get more accurate location results is included View full abstract»

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  • Near-minimum-time task planning for fruit-picking robots

    Page(s): 48 - 56
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    A near-minimum-time task-planning algorithm for fruit-harvesting robots having to pick fruits at N given locations is presented. For the given kinematic and inertial parameters of the manipulator, the algorithm determines the near-optimal sequence of fruit locations through which the arm should pass and finds the near-minimum-time path between these points. The sequence of motions was obtained by solving the traveling salesman problem (TSP) using the distance along the geodesics in the manipulator's inertia space, between every two fruit locations, as the cost to be minimized. The proposed algorithm was applied to define the motions of a citrus-picking robot and was tested for a cylindrical robot on fruit position data collected from 20 trees. Significant reduction in the required computing time was achieved by dividing the volume containing the fruits into subvolumes and estimating the geodesic distance rather than calculating it View full abstract»

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  • Real-time communications in a computer-controlled workcell

    Page(s): 105 - 113
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    A computer-integrated manufacturing (CIM) system is composed of several workcells, each of which contains robots, numerical-control machines, sensors, and a transport mechanism. The author considers a communication subsystem that is designed to support real-time control and coordination of devices in each CIM cell. The concept of a poll number is proposed to control the access to the intracell bus. The bus access mechanism with the poll number is intended to minimize the probability of real-time messages missing their deadlines. Use of a poll number provides not only for decentralized control of the intracell bus, but also a high degree of flexibility in scheduling messages. The performance of the bus access mechanism with a poll number is analyzed and compared with that of a token bus which is widely used in CIM systems such as MAP (Manufacturing Automation Protocol) networks. The probability of a real-time message missing its deadline in a token bus is found to be much higher than that of the proposed mechanism View full abstract»

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  • A parallel algorithm for incremental stereo matching on SIMD machines

    Page(s): 123 - 134
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    An effort has been made to develop a robust high-speed stereo matcher by exploiting parallel algorithms executing on general-purpose SIMD machines. This approach is based on several existing techniques dealing with the classification and evaluation of matches, the application of ordering constraints, and relaxation-based matching. The techniques have been integrated and reformulated in terms of parallel execution on a theoretical SIMD machine. An ideal machine topology for executing this parallel algorithm is identified through complexity analysis. Feasibility is demonstrated by implementation on a commercially available SIMD machine, and its performance is compared with that of the idealized machine. Sample results are shown for real and synthetic stereo pairs View full abstract»

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  • Performance analysis of synchronous production lines

    Page(s): 1 - 8
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    In synchronous production lines, the transfer of all parts in the line takes place simultaneously. If one workstation breaks down, the whole line will be shut down for repair. The authors consider modeling the performance of such lines with random line stoppages, scrapping of parts, and a limited number of operators available for clearing workstations. An analytical model is proposed for this purpose. In the single operator case, the model is free of any distributional assumptions. For the multiple operator case, an exponential assumption is required for an exact analysis, but simple performance bounds are derived for the general case. Some numerical examples are presented View full abstract»

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  • An automatic navigation system for vision guided vehicles using a double heuristic and a finite state machine

    Page(s): 181 - 189
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    A navigation system for automatic vision-guided vehicles which uses an efficient double heuristic search algorithm for path planning is presented. It is capable of avoiding unknown obstacles and recovering from unidentifiable locations. A linked list representation of the path network database makes the implementation feasible in any high-level language and renders it suitable for real-time application. Extensive simulated experiments have been conducted to verify the validity of the proposed algorithms. The combination of the techniques of robot navigation in unexplored terrain and the global map method proved to be a valid technique for automated guided vehicle (AGV) guidance. A learning mechanism is used in the AGV by updating the path network during navigation. Simulated results supported all the theoretically expected conclusions, since the robot planned its path correctly between the requested nodes and maneuvered its way around the obstacles. Overall, the results were very encouraging View full abstract»

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  • Weighted selection of image features for resolved rate visual feedback control

    Page(s): 31 - 47
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    The authors develop methodologies for the automatic selection of image features to be used to visually control the relative position and orientation (pose) between the end-effector of an eye-in-hand robot and a workpiece. A resolved motion rate control scheme is used to update the robot's pose based on the position of three features in the camera's image. The selection of these three features depends on a blend of image recognition and control criteria. The image recognition criteria include feature robustness, completeness, cost of feature extraction, and feature uniqueness. The control criteria include system observability, controllability, and sensitivity. A weighted criteria function is used to select the combination of image features that provides the best control of the end-effector of a general six-degrees-of-freedom manipulator. Both computer simulations and laboratory experiments on a PUMA robot arm were conducted to verify the performance of the feature-selection criteria View full abstract»

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  • Effect of motor dynamics on nonlinear feedback robot arm control

    Page(s): 114 - 122
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    A nonlinear feedback robot controller that incorporates the robot manipulator dynamics and the robot joint motor dynamics is proposed. The manipulator dynamics and the motor dynamics are coupled to obtain a third-order-dynamic model, and differential geometry control theory is applied to produce a linearized and decoupled robot controller. The derived robot controller operates in the robot task space, thus eliminating the need for decomposition of motion commands into robot joint space commands. Computer simulations are performed to verify the feasibility of the proposed robot controller. The controller is further experimentally evaluated on the PUMA 560 robot arm. The experiments show that the proposed controller produces good trajectory tracking performances and is robust in the presence of model inaccuracies. Compared with a nonlinear feedback robot controller based on the manipulator dynamics only, the proposed robot controller yields conspicuously improved performance View full abstract»

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  • An inherent stability problem in Cartesian compliance and an alternative structure of compliance control

    Page(s): 21 - 30
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    Active compliance is often used in the control of the legs of a walking machine to allow a vehicle to adapt to terrain irregularity. This technique balances force and position errors in Cartesian space to achieve the operation of a damped spring. It is shown that, when decomposed into individual actuator systems, Cartesian compliance may require positive feedback of the equivalent joint torque error to a certain joint. Thus, such a joint can be locally unstable if the environment which the leg system contacts is not passively compliant enough. An inherent stability problem associated with this Cartesian-space compliance control is investigated, and an alternative structure of compliance control that eliminates the inherent source of instability and still permits adaptability to terrain irregularity is introduced. The new algorithm was implemented on the Ohio State University Hexapod vehicle and experimentally verified as giving better performance in system stability than the existing Cartesian compliance algorithm View full abstract»

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  • Modeling flexible manufacturing systems: the concurrent logic programming approach

    Page(s): 135 - 148
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    A novel approach to the modeling and analysis of an FMS (flexible manufacturing system) is presented, focusing on shop-floor control processes. This approach is based on concurrent logic programming, which uses the theoretical foundation of communicating sequential processes and guarded commands with nondeterminacy. The modeling approach is implemented using Flat Concurrent Prolog (FCP) on a Sun workstation or on a VAX machine. The properties of concurrent logic programming, as demonstrated by using FCP, include: (1) hierarchical description; (2) support for timing specifications; (3) modeling of concurrency and synchronization; (4) support for generic modeling; (5) facilitation of data transfer and complex communication; (6) capability of performance evaluation; (7) capability of static and dynamic analysis; (8) debugging capabilities; and (9) simulation ability View full abstract»

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  • New heuristic algorithms for efficient hierarchical path planning

    Page(s): 9 - 20
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    The authors consider one of the most popular approaches to path planning: hierarchical approximate cell decomposition. This approach consists of constructing successive decompositions of the robot's configuration space into rectangloid cells and searching the connectivity graph built at each level of decomposition for a path. Despite its conceptual simplicity, an efficient implementation of this approach raises many delicate questions that have not yet been addressed. The major contributions this work are (1) a novel approach to cell decomposition based on constraint reformulation and (2) a new algorithm for hierarchical search with a mechanism for recording failure conditions. These algorithms have been implemented in a path planner, and experiments with this planner have been carried out on various examples. These experiments show that the proposed planner is significantly (approximately 10 times) faster than previous planners based on the same general approach 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