bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parallel computation of symbolic robot models and control laws: Theory and application to transputer networks
Authors: Kirćanski N. , Petrović T. , Vukobratović M. 
Published: July 2007

AbstractNew computer architectures based on large numbers of processors are now used in various application areas ranging from embedded systems to supercomputers. Efficient parallel processing algorithms are applied in a wide variety of applications such as simulation, robot control, and image synthesis. This article presents two novel parallel algorithms for computing robot inverse dynamics (as well as control laws) starting from customized symbolic robot models. To gain the most benefit from the concurrent processor architecture, the whole job is divided into a large number of simple tasks, each involving only a single floating‐point operation. Although requiring sophisticated scheduling schemes, fine granularity of tasks was the key factor for achieving nearly maximum efficiency and speedup.The first algorithm resolves the scheduling problem for an array of pipelined processors. The second one is devoted to parallel processors connected by a complete crossbar interconnection network. The main feature of the proposed algorithms is that they take into account the communication delays between processors and minimize both the execution time and communication cost. To prove the theoretical results, the algorithms have been verified by experiments on an INMOS T800 transputer‐based system. We used four transputers in serial and parallel configurations. The experimental results show that the most complicated dynamic control laws can be executed in a submilisecond time interval. © 1993 John Wiley & Sons, Inc.
Method for kinematic calibration of stewart platforms
Authors: Zhuang Hanqi , Roth Zvi S. 
Published: July 2007

AbstractA Stewart platform is a six degrees of freedom parallel manipulator composed of six variable‐length legs connecting a fixed base to a movable plate. Like all parallel manipulators, Stewart platforms offer high force/torque capability and high structural rigidity in exchange for small workspace and reduced dexterity. Because the solution for parallel manipulators' forward kinematics is in general much harder than their inverse kinematics, a typical control strategy for such manipulators is to specify the plate's pose in world coordinates and then solve the individual leg lengths. The accuracy of the robot critically depends on accurate knowledge of the device's kinematic parameters. This article focuses on the accuracy improvement of Stewart platforms by means of calibration.Calibration of Stewart platforms consists of construction of a kinematic model, measurement of the position and orientation of the platform in a reference coordinate frame, identification of the kinematic parameters, and accuracy compensation. A measurement procedure proposed in this article allows a great simplification of the kinematic identification. The idea is to keep the length of the particular leg, whose parameters are to be identified, fixed while the other legs change their lengths during the measurement phase. By that, redundant parameters can be eliminated systematically in the identification phase. The method also shows the estimation of each leg's parameters separately because the measurement equations are fully decoupled, which results in a drastical reduction of the computational effort in the parameter identification. Simulation results assess the performance of the proposed approach. © 1993 John Wiley & Sons, Inc.
A family of stewart platforms with optimal dexterity
Authors: Pittens Kenneth H. , Podhorodeski Ron P. 
Published: July 2007

AbstractStewart platform configurations (architectures and poses) optimizing local dexterity are investigated. The condition number of the Jacobian matrix is used to quantify the dexterity of the manipulator. For a platform‐centered Jacobian reference location and a given characteristic length for scaling purposes, a two‐parameter family of optimal configurations is shown to exist. Two suitable architectural parameters defining the family are identified and properties of the optimal configurations are discussed. The optimization results are shown to be easily extended for other Jacobian reference locations and for other singular value‐based local dexterity measures. It is suggested that the existence of a two‐parameter family of optimal local configurations could be exploited to aid in the resolution of optimal architectures for global measures.
Review and unification of reduced‐order force control methods
Authors: Grabbe M. T. , Carroll J. J. , Dawson D. M. , Qu Z. 
Published: July 2007

AbstractIn this article, we compare some of the recent methods developed for simultaneous position and force control of a single n‐link constrained robot manipulator. Mathematical models of the constrained manipulator are introduced and the advantages and disadvantages of the associated control formulations are discussed. The similarities between each of the proposed formulations are also highlighted. Finally, a transformation is presented that generalizes the methods of decoupling force from the position dynamics.
Dynamic analysis and control of a stewart platform manipulator
Authors: Lebret G. , Liu K. , Lewis F. L. 
Published: July 2007

AbstractThe Stewart platform is a six‐axis parallel robot manipulator with a force‐to‐weight ratio and positioning accuracy far exceeding that of a conventional serial‐link arm. Its stiffness and accuracy approach that of a machine tool yet its workspace dexterity approaches that of a conventional manipulator. In this article, we study the dynamic equations of the Stewart platform manipulator. Our derivation is closed to that of Nguyen and Pooran because the dynamics are not explicitly given but are in a step‐by‐step algorithm. However, we give some insight into the structure and properties of these equations: We obtain compact expressions of some coefficients. These expressions should be interesting from a control point of view. A stiffness control scheme is designed for milling application. Some path‐planning notions are discussed that take into account singularity positions and the required task. The objective is to make the milling station into a semiautonomous robotic tool needing some operator interaction but having some intelligence of its own. It should interface naturally with part delivery and other higher‐level tasks.
Exact methods for determining the kinematics of a stewart platform using additional displacement sensors
Authors: Cheok Ka C. , Overholt James L. , Beck Ronald R. 
Published: July 2007

AbstractThe Stewart platform (SP) is a parallel closed‐kinematic chain robotic mechanism that is capable of providing high structural and positional rigidity. Because of its unique capability, the platforms have been employed in many control engineering applications such as simulator shakers, robotic manipulators, etc. However, a main problem often found in the implementation of a real‐time controller for the platform is the lack of an efficient algorithm for solving its highly nonlinear forward kinematic transformation (FKT), where one seeks to find the translational and orientational altitudes of the moveable platform from knowing the lengths of the platform linkages. This article describes two new direct and exact methods for computing the translational and rotational displacements of an SP by employing extra transnational displacement sensors (TDSs), in addition to the existing TDSs for the six links of the SP. The key for the approach lies in knowing where to employ the TDSs for determining positional vectors of strategic platform locations. By taking advantage of a tetrahedral geometry, closed‐form solutions for the FKT can then be derived and directly evaluated. The new methods produce accurate solutions with only minimal computation necessary. The advantages and disadvantages of the proposed methods are discussed and compared to an existing method. The exact methods are being investigated for an on‐line implementation of a nonlinear adaptive control system and redundancy scheme for a 25‐ton Stewart platform‐based Crew Station/Turret Motion Base Simulator (CS/TMBS) at the U.S. Army Tank‐Automotive Command (TACOM).
The NIST robocrane
Authors: Albus James , Bostelman Roger , Dagalakis Nicholas 
Published: July 2007

AbstractThe Robot Systems Division of the National Institute of Standards and Technology (NIST) has been experimenting for several years with new concepts for robot cranes. These concepts utilize the basic idea of the Stewart platform parallel link manipulator. The unique feature of the NIST approach is to use cables as the parallel links and to use winches as the actuators. As long as the cables are all in tension, the load is kinematically constrained and the cables resist perturbing forces and moments with equal stiffness to both positive and negative loads. The result is that the suspended load is constrained with a mechanical stiffness determined by the elasticity of the cables, the suspended weight, and the geometry of the mechanism. Based on these concepts, a revolutionary new type of robot crane, the NIST ROBOCRANE, has been developed that can control the position, velocity, and force of tools and heavy machinery in all six degrees of freedom (x, y, z, roll, pitch, and yaw). Depending on what is suspended from its work platform, the ROBOCRANE can perform a variety of tasks. Examples are: cutting, excavating and grading, shaping and finishing, lifting, and positioning. A 6‐m version of the ROBOCRANE has been built and critical performance characteristics analyzed.
Six‐degree‐of‐freedom active vibration isolation using a stewart platform mechanism
Authors: Geng Zheng , Haynes Leonard S. 
Published: July 2007

AbstractIntelligent Automation, Inc. has performed a study of a six‐degree‐of‐freedom (dof) active vibration isolation system based on a Stewart platform mechanism to be used for precision control of a wide range of space‐based structures as well as earth‐based systems. This article presents part of the study results, which includes a new Terfenol‐D actuator design and analysis, a design of a Stewart platform as a vibration isolation device, and robust adaptive filter algorithms for active vibration control. Prototype hardware of a six‐dof active vibration isolation system has been implemented and tested. About 30 dB of vibration attenuation is achieved in real‐time experiments.
Single‐input/single‐output transfer functions for a flexible slewing link
Authors: Barbieri Enrique 
Published: July 2007

AbstractTruncated linear models based on constrained and unconstrained mode expansions for a flexible link with torque actuation at its hub led us to examine the behavior of theopen‐loop‐zerosof five commonly used single‐input single‐output transfer functions. We arrive at new conclusions with regard to minimum‐ and non‐minimum‐phase zeros, and passivity of the transfer functions. The flexible‐to‐rigid inertia (FRI) ratio plays an important role in the determination of these characteristics. This article illustrates how the zero locations of some of the transfer functions are dramatically affected by the FRI ratio. We also investigate the performance of a hub angle, hub rate, and relative tip position static feedback controller based on a reduced‐orderconstrainedmode model when applied to both unconstrained and constrained mode models of the same dimension. Simulations indicate that the constrained model can be stable while the unconstrained model is not for high FRI ratios. Our findings can provide useful information to designers in cases where the controller is sensitive to the location of the plant's zeros.
Friction modeling and compensation for an industrial robot
Authors: Phillips Stephen M. , Ballou Kevin R. 
Published: July 2007

AbstractThis article describes the detailed friction modeling of the General Electric GP132 industrial robot. Friction is an area whose importance is often discounted in the development of control systems because it is thought to be insignificant or unmodelable. This work demonstrates that friction does have a predictable structure, and that significant performance improvement can be realized through its proper compensation. Experiments performed to determine the static, Coulomb, and viscous friction of the GP132 are presented. In addition to these components, the robot is shown to have significant gravity load‐dependent and position‐dependent friction. The accuracy of the friction models are verified through several experiments and are shown to be considerably better than previously formulated models.
New approach for aggregating multi‐sensory data
Authors: Basir O. A. , Shen H. C. 
Published: July 2007

AbstractThe task of sensory data fusion may involve the aggregation of sensory measurements that may be from different phenomenological domains and that, in many cases, could embrace some conflicting information cues. It is rather a challenge to find suitable strategies by which measurements obtained by the different sensors of the system can be aggregated so that a consistent interpretation of these measurements is achieved. In this article, we present a novel approach to achieve this goal. A recursive group utility function that is capable of bringing the group of sensors into consensus is used. After each sensor in the group gathers information relevant to the sensory task, the group engages in what we call the uncertainty estimation stage. This is an information theorybased process that allows each sensor to assess its self‐uncertainty and the conditional uncertainties of other sensors. This process facilitates the computation of a weighting scheme that operates recursively on sensor observations until the group reaches a consensus. Whenever new observations are made, the uncertainty estimates of sensors are updated and used to compute a new weighting scheme. To demonstrate the efficacy and to show how the methodology works, the article discusses how the method can be used to tackle the multi‐sensor object identification problem. © 1993 John Wiley & Sons, Inc.
Efficient robot arm modeling for computer control
Authors: Megahed Said M. 
Published: July 2007

AbstractThis article presents a comparative study of the required number of arithmetic operations necessary for computing robot arm models using the Denavit‐Hartenberg symbolic notation and a proposed one. The proposed notation is based on the idea of describing the motion of a robot joint by a pair matrix and the geometry of a link by a shape matrix. This notation needs the use of two coordinate systems for each joint or link. The results prove that the proposed notation reduces the computation time of robot models. For a 6‐degrees of freedom robot arm, the computation times of kinematic position, velocity, and dynamic models are reduced respectively by 20%, 5%, and 2%, respectively. The two notations have the same effects on computing the inverse models. © 1993 John Wiley & Sons, Inc.
Reactive behaviors of fast mobile robots
Authors: Zapata René , Lépinay P. , Thompson P. 
Published: July 2007

AbstractThis article addresses the modeling of the reactive behaviors of a mobile robot moving in unstructured and dynamic environments. The main focus is on the software structure devoted to obstacle avoidance when geometric models do not exist and when obstacles can be dynamic. The first part concerns the model of the robot/environment interaction. This model is based on the definition of theinteraction component(deformable virtual zone) of aninternal stateof the robot and leads to avoidance‐oriented control laws. The second part describes the derivation of the state equation and one of its implementations on a fast outdoor mobile robot. © 1994 John Wiley & Sons, Inc.
Identification of a trajectory generator model for the PUMA‐560 robot
Authors: Tondu Bertrand , El‐zorkany Hany 
Published: July 2007

AbstractIn this article, work on the experimental identification of a model of the trajectory generator of a PUMA‐560 robot is reported. The model developed is based on theoretical work reported in the literature and the necessary parameters are obtained experimentally. The resulting model is validated versus the corresponding actual robot motions. All experiments are based on the use of a 3D non‐contact position sensor to record the motions of the robot end‐effector. © 1994 John Wiley & Sons, Inc.
Effect of tension parameters and intervals on splines‐under‐tension based robot trajectory planning
Authors: Yi Seung‐Jong , Kim Kyuil 
Published: July 2007

AbstractThe new trajectory planner using cubic spline functions under tension in joint coordinates is developed and implemented in the 6 dof articulated robot with a parallel drive arm mechanism to improve the smoothness of the joint trajectories and positioning accuracy of the manipulator. Also, the optimal selection of the tension parameter and time interval selection schemes are investigated in this study. © 1994 John Wiley & Sons, Inc.
Design and control of a three‐degrees‐of‐freedom, in‐parallel, actuated manipulator
Authors: Pfreundschuh George H. , Sugar Thomas G. , Kumar Vijay 
Published: July 2007

AbstractThe mechanics, design, and control of a 3–degrees‐of‐freedom, in‐parallel, pneumatically actuated manipulator are presented. The manipulator consists of two platforms connected by three serial chains. The kinematic design is such that the three relative degrees of freedom between the two plates allow the manipulator to accomodate uncertainties and sustain impacts while contacting and interacting with unknown environments. In particular, the manipulator is naturally compliant in translation along the approach direction as well as in rotations about axes perpendicular to the approach direction, while it is stiff in other directions. In this article, an overview of the manipulator kinematics, a description of the manipulator system and the associated hardware, and experimental results on the dynamic behavior of a prototype are presented. © 1994 John Wiley & Sons, Inc.
Inverse kinematics of planar redundant manipulators via virtual links with configuration index
Authors: Chung W. J. , Youm Y. , Chung W. K. 
Published: July 2007

AbstractThis article presents a new method for generating inverse kinematic solutions for planar manipulators with large redundancy (hyper‐redundant manipulators). The proposed method starts by decomposing a planar redundant manipulator into a series of local planar arms that are either 2‐link or 3‐link manipulator modules, and connecting the conjunction points between them with virtual links. The manipulator then can be handled by a simple virtual link system, which may be conveniently divided into non‐singular and singular cases depending on its configuration. When the virtual link system is no longer effective due to a singular configuration, the displacement of the end‐effector is then allocated to virtual links according to a displacement distribution criterion. A dexterity index called the “configuration index” distinguishes the non‐singular and singular cases. The concept of virtual link is shown by computer simulations to be simple and effective for the inverse kinematics of a planar hyper‐redundant manipulator with a discrete model. In particular, it can be applied to solving the inverse kinematics of a SCARA‐type spatial redundant manipulator whose redundancy is included in its planar mechanism. © 1994 John Wiley & Sons, Inc.
Mobile manipulator path planning by a genetic algorithm
Authors: Zhao Min , Ansari Nirwan , Hou Edwin S. H. 
Published: July 2007

AbstractThis article addresses the path‐planning problem for a mobile manipulator system that is used to perform a sequence of tasks specified by locations and minimum oriented force capabilities. The problem is to find an optimal sequence of base positions and manipulator configurations for performing a sequence of tasks given a series of task specifications. The formulation of the problem is nonlinear. The feasible regions for the problem are nonconvex and unconnected. Genetic algorithms applied to such problems appear to be very promising while traditional optimization methods cause difficulties. Computer simulations are carried out on a three‐degrees‐of‐freedom manipulator mounted on a two‐degrees‐of‐freedom mobile base to search for the near optimal path‐planning solution for performing the sequence of tasks. © 1994 John Wiley & Sons, Inc.
Navigation control for a mobile robot
Authors: Han Min‐Hong , Rhee Sang‐Yong Rhee 
Published: July 2007

AbstractThis article describes a navigation method of a mobile robot which uses a single camera and a guide mark. A travel path is instructed to the robot by means of path drawn on a monitor screen. The image of the guide mark provides information regarding the robot's position and heading direction. The heading direction is adjusted while moving if any deviation from the specified path is detected. The proposed method has been implemented in a mobile robot which runs at the average speed of 2.5 ft/s. without deviating more than one foot from the specified path in an indoor environment. © 1994 John Wiley & Sons, Inc.
Model‐based location of automated guided vehicles in the navigation sessions by 3d computer vision
Authors: Lee Pai‐Shih , Shen Yuh‐Erl , Wang Ling‐Ling 
Published: July 2007

AbstractA model‐based approach to determining the location of an automated guided vehicle (AGV) in the navigation session is proposed. Significant scenes along the navigation path are taken and stored as model images. Also, specific templates of each model image are chosen in advance for matching. When the AGV approaches one significant scene in the navigation session, an input image is taken and the corresponding model image is fetched. Each template in the model image is matched with the input image through the use of the three‐step method. The templates are directly used for matching; therefore, no special image processing techniques are required for the input image in the navigation session. In addition, several templates in a model image are used for matching instead of the model image itself. This promotes the robustness of the matching results and saves the computation cost. Furthermore, the 2D string method is used as a post‐verifier to discard erroneous matching results. The remaining correct matching results then can be used to determine the vehicle location on the navigation path. Simulated experiments are implemented and the results confirm the feasibility of the proposed approach. © 1994 John Wiley & Sons, Inc.
Convergence and robustness of a discrete‐time learning control scheme for constrained manipulators
Authors: Cheah C. C. , Wang Danwei , Soh Y. C. 
Published: July 2007

AbstractThe constrained motion control is one of the most common control tasks found in many industrial robot applications. The nonlinear and nonclassical nature of the dynamic model of constrained robots make designing a controller for accurate tracking of both motion and force a difficult problem. In this article, a discrete‐time learning control problem for precise path tracking of motion and force for constrained robots is formulated and solved. The control system is able to reduce the tracking error iteratively in the presence of external disturbances and errors in initial condition as the robot repeats its action. Computer simulation result is presented to demonstrate the performance of the proposed learning controller. © 1994 John Wiley & Sons, Inc.