bluuebunny/crossref_metadata_2025_split huggingface dataset:
A multivariable control scheme for robot manipulators
Authors: Tarokh M. , Seraji H. 
Published: July 2007

AbstractThe article puts forward a simple scheme for multivariable control of robot manipulators to achieve trajectory tracking. The scheme is composed of an inner loop stabilizing controller and an outer loop tracking controller. The inner loop utilizes a multivariable PD controller to stabilize the robot by placing the poles of the linearized robot model at some desired locations. The outer loop employs a multivariable PID controller to achieve input‐output decoupling and trajectory tracking. The gains of the PD and PID controllers are related directly to the linearized robot model by simple closed‐form expressions. The controller gains are updated on‐line to cope with variations in the robot model during gross motion and for payload change. Alternatively, the use of high gain controllers for gross motion and payload change is discussed. Computer simulation results are given for illustration.
Principle and applications of retroreflective vision sensing for discrete part‐presentation
Authors: Lee Kok‐Meng , Li Da‐Rein 
Published: July 2007

AbstractFor flexible manufacturing of short production runs where a large variety of product sizes, component types, and surface reflectance characteristics are encountered, it is desirable to build flexible computer‐controlled systems for feeding parts into machine tools or assembly processes that combine maximum flexibility and reliability with minimum cost and cycle‐time. This is not a general bin‐picking problem; the parts are assumed to be propositioned approximately in totes/pallets/kits with regularly spaced locations. This article presents a machine vision technique based on the principle of retroreflective vision sensing for part‐presentation. Since retroreflective material has a distinctive surface reflectance that is not commonly found in natural or man‐made objects, the use of retroreflective surfaces enables reliable high object‐to‐background contrast images to be obtained for a wide variety of objects. Unlike conventional machine vision techniques, which rely on the variance of the surface reflectance of the objects to generate detailed images, retroreflective vision sensing aims at generating a reliable two‐dimensional digital object silhouettes so that the location and orientation of the part can be reliably determined. Two application examples, machine loading and assembly, are illustrated.
Improving local torque optimization techniques for redundant robotic mechanisms
Authors: Ma Shugen , Hirose Shigeo , Nenchev Dragomir N. 
Published: July 2007

AbstractTwo techniques that improve existing local torque optimization methods for redundant robotic mechanisms are proposed. The first technique is based on a balancing scheme, which balances a joint torque norm against a norm of joint accelerations. Expressions have been derived utilizing the Lagrangian multipliers method. The other technique is based on a torque optimization method which minimizes torques through accelerations, obtained from the null‐space of the Jacobian matrix. These accelerations are balanced against the minimum‐norm acceleration component in order to improve the performance. Numerical simulations have been carried out which in most cases illustrate good performance capability from the viewpoint of torque optimization and global stability.
New inverse kinematic algorithms for redundant robots
Authors: Hsia T. C. , Guo Z. Y. 
Published: July 2007

AbstractNew inverse kinematic algorithms for generating redundant robot joint trajectories are proposed. The algorithms utilize the kinematic redundancy to improve robot motion performance (in joint space or Cartesian space) as specified by certain objective functions. The algorithms are based on the extension of the existing “joint‐space command generator” technique in which a null space vector is introduced which optimizes a specific objective function along the joint trajectories. In this article, the algorithms for generating the joint position and velocity (PV) trajectories are extensively developed. The case for joint position, velocity, and acceleration (PVA) generation is also addressed. Application of the algorithms to a four‐link revolute planar robot manipulator is demonstrated through simulation. Several motion performance criteria are considered and their results analyzed.
A study of robot inverse kinematics based upon the solution of differential equations
Authors: Cheng H. , Gupta K. C. 
Published: July 2007

AbstractThis article presents an improved numerical algorithm for robot inverse kinematics which is based upon the solution of the first‐order differential equations arising from the manipulator's velocity Jacobian relations. The use of the Adams‐Moulton predictorcorrector scheme leads to a fourth‐order trajectory following in the joint space. The implementation of a strict descent feature for the trajectory error at the end‐effector level contributes to the robustness of the algorithm near singularities. The execution of this algorithm is about 2.7 times faster than that of Gupta and Kazerounian,16with much of the speed up coming from the use of software optimizations. Several issues related to the accuracy, convergence, speed, real‐time computation, and portability of this algorithm are discussed.
Navigation strategies for multiple autonomous mobile robots moving in formation
Authors: Wang P. K. C. 
Published: July 2007

AbstractThe problem of deriving navigation strategies for a fleet of autonomous mobile robots moving in formation is considered. Here each robot is represented by a particle with a spherical effective spatial domain and a specified cone of visibility. The global motion of each robot in the world space is described by the equations of motion of the robot's center of mass. First, methods for formation generation are discussed. Then, simple navigation strategies for robots moving in formation are derived. A sufficient condition for the stability of a desired formation pattern for a fleet of robots each equipped with the navigation strategy based on nearest neighbor tracking is developed. The dynamic behavior of robot fleets consisting of three or more robots moving in formation in a plane is studied by means of computer simulation.
An improved method for on‐line calculation and compensation of the static deflection at a robot end‐effector
Authors: Lin Paul P. , Chiang Hsiang‐Dih , Cui Xiu Xun 
Published: July 2007

AbstractTraditionally, robotic deflection analysis for a low‐weight robot has been performed based on an assumption that each link is treated as a cantilever beam, which leads to no angular deflection at a joint. In practice, a robotic intermediate joint is linearly and angularly deflected when a load is applied at the end‐effector. It is found in this study that the additional link deflection resulting from the angular deflection of a robotic revolute joint substantially contributes to the end‐effector's total deflection. This article presents an improved method via a combination of classical beam theory, energy methods and the concepts of differential relationships to more accurately calculate the static deflection at the end‐effector. A systematic approach to deflection calculation through three different Jacobians are presented. The study also shows that the end‐effector's deflection heavily depends on robotic arm configurations. The deflection is then compensated based on the selected optimum configuration. The theoretical deflection analysis is verified by experimental results. A planar two‐link robot and a six‐degree‐of‐freedom Elbow Manipulator are used for numerical illustration and calculation procedure.
A coordinated control of an underwater vehicle and robotic manipulator
Authors: Mahesh H. , Yuh J. , Lakshmi R. 
Published: July 2007

AbstractRemotely operated underwater robotic vehicles (URVs) have been used for various tasks: inspection, recovery, construction, etc. With the increased utilization of remotely operated vehicles in subsea applications, the development of autonomous vehicles becomes highly desirable to enhance operator efficiency. However, engineering problems associated with the high density, nonuniform and unstructured seawater environment, and the nonlinear response of the vehicle make a high degree of autonomy difficult to achieve. The vehicles are usually equipped with mechanical manipulators that are utilized during the working mode. The accurate performance of the vehicle during the working mode can be achieved by controlling the vehicle and manipulator at the same time and compensating the end‐effector error due to the vehicle motion. This article describes an adaptive control strategy for the coordinated control of an underwater vehicle and its robotic manipulator. The effectiveness of the control system is investigated by case study. The results show that the presented control system can provide the high performance of the vehicle and manipulator in the presence of unpredictable changes in the dynamics of the vehicle and its environment.
Adaptive control of nonlinear systems: A case study of underwater robotic systems
Authors: Fossen Thor I. , Sagatun Svein I. 
Published: July 2007

AbstractThe problem of controlling underwater mobile robots in 6 degrees of freedom (DOF) is addressed. Underwater mobile robots where the number of thrusters and control surfaces exceeds the number of controllable DOF are considered in detail. Unlike robotic manipulators underwater mobile robots should include a velocity dependent thruster configuration matrixB(q), which modifies the standard manipulator equation to:Mq+C(q)q+g(x)=B(q)uwherex=J(x)q. Uncertainties in the thruster configuration matrix due to unmodeled nonlinearities and partly known thruster characteristics are modeled as multiplicative input uncertainty. This article proposes two methods to compensate for the model uncertainties: (1) an adaptive passivity‐based control scheme and (2) deriving a hybrid (adaptive and sliding) controller. The hybrid controller combines the adaptive scheme whereM, C, andgare estimated on‐line with a switching term added to the controller to compensate for uncertainties in the input matrixB.Global stability is ensured by applying Barbalat's Lyapunov‐like lemma. The hybrid controller is simulated for the horizontal motion of the Norwegian Experimental Remotely Operated Vehicle (NEROV).
A new method for the geometric modeling of lower pairs and its application to the kinematic spaces of spatial robots
Authors: Yih T. C. 
Published: July 2007

AbstractA new notation is developed to model and analyze spatial robots. This method is formulated based on the homogeneous cylindrical coordinates and Bryant angles transformation matrices and thus termed “C‐B notation.” At first, shape matrix for a binary link is derived. Then, the characteristic matrices for the five most commonly used kinematic lower pairs—revolute (R), prismatic (P), cylindrical (C), helical (H), and spherical (S)—are formulated. The “exact” joint positions, that is, the actual location of the physical joint center in space, can be defined using this method. The governing kinematic equations for the analysis of spatial robots are derived as well. Finally, the “kinematic spaces” for the open‐chain robot are defined as “the group of space of work (displacement) space, velocity space (the velocity envelope in the displacement differentialVx‐Vy‐Vzcoordinates), and acceleration space (the acceleration envelope in the velocity differentialAx‐Ay‐Azcoordinates).” Numerical examples for parallel projections of kinematic spaces on both sagittal and frontal planes are illustrated by the industrial Unimate 2000 spherical (SP/RRR) robot, Bendix AA/CNC (RRP/RRR) robot, and 6R Cincinnati Milacron T3 robot.
Numerical calculation of the base inertial parameters of robots
Authors: Gautier M. 
Published: July 2007

AbstractThis article presents a new approach to the problem of determining the minimum set of inertial parameters of robots. The calculation is based on numerical QR and SVD factorizations and on the scaling procedure of matrices. It proceeds in three steps:eliminate standard inertial parameters which have no effect on the dynamic model,determine the number of base parameters,anddetermine a set of base parameters by regrouping some standard parameters to some others in linear relations.Different models, linear in the inertial parameters are used: a complete dynamic model, a simplified dynamic model, and an energy model. The method is general, it can be applied to open loop, or graph‐structured robots. The algorithms are easy to implement. An application for the PUMA 560 robot is given.
A general force/torque relationship and kinematic representation for flexible link manipulators
Authors: Kozel D. , Koivo A. J. , Mahil S. S. 
Published: July 2007

AbstractA technique to determine the relationship between the generalized joint torque and the generalized force exerted by the end‐effector of a flexible link manipulator on the environment is presented. First, a systematic technique which accounts for the links' bending and torsion is used to determine the kinematic equations of the manipulator. A procedure to determine a “pseudo” Jacobian matrix which accounts for the links' flexibility is then developed. In the determination of the pseudo Jacobian matrix, partial derivatives are not used, thus reducing inaccuracies resulting from approximating the bending and torsion of the links. Using the principle of virtual work, a force and torque relationship between the joints and end‐effector is obtained. To demonstrate the validity of the technique presented, computer simulations of the resulting force/torque relationship are compared to results obtained experimentally.
3‐D curve matching using splines
Authors: Kishon Eyal , Hastie Trevor , Wolfson Haim 
Published: July 2007

AbstractA machine vision algorithm to find the longest common subcurve of two 3‐D curves is presented. The curves are represented by splines fitted through sequences of sample points extracted from dense range data. The approximated 3‐D curves are transformed into 1‐D numerical strings of rotation and translation invariantshape signatures, based on a multiresolution representation of the curvature and torsion values of the space curves. Theshape signaturestrings are matched using an efficient hashing technique that finds longest matching substrings. The results of the string matching stage are later verified by a robust, least‐squares, 3‐D curve matching technique, which also recovers the Euclidean transformation between the curves being matched. This algorithm is of average complexityO(n)wherenis the number of the sample points on the two curves. The algorithm has applications in assembly and object recognition tasks. Results of assembly experiments are included.
Discrete‐time adaptive control for mechanical manipulators having a joint compliance
Authors: Yuh J. , Tissue Deborah K. 
Published: July 2007

AbstractThis paper presents the application of a discrete‐time adaptive control scheme to mechanical manipulators having a joint compliance. A control model of such manipulators is derived by linearizing the nonlinear equations about a desired trajectory. This control model is described by multivariable difference equations. The parameters of the model are estimated by parameter adaptation algorithms. Control gains, determined from the control model by using the pole placement technique, are computed on‐line with the estimates of the system parameters. Simulation results with a two‐link mechanical manipulator are presented to show the effectiveness of the proposed approach.
On the connectivity of manipulator free workspace
Authors: Wenger P. , Chedmail P. 
Published: July 2007

AbstractThis article presents a new topological characterization of the free workspace of manipulators moving among obstacles. The free workspace is the set of positions and orientations that the end‐effector of the manipulator can reach, according to the joint limits of each of its links, and taking into account the obstacles of the environment. A classification of new connectivity properties of the free workspace is proposed, corresponding to different types of motions (point‐to‐point motions, following of continuous trajectories) that the manipulator can perform in the Cartesian space. For each property, a necessary and sufficient condition is given, which permits verification of the connectivity of the whole free workspace and leads to all the connected subspaces in it. These properties have been implemented in a Robotics C.A.D. system using octree representation of spaces. Some applications are presented, which show that this work is of primary interest for preparing off‐line tasks, and is a new contribution to the problem of robotic cell layout design.
Path planning and gait of walking machine in an obstacle‐strewn environment
Authors: Lee Jong‐Kil , Song Shin‐Min 
Published: July 2007

AbstractThe locomotion of a quadrupedal walking machine in an obstacle‐strewn environment is studied. The path planning of the walking machine body includes the following two features: first, the path is generated based on the Bezier curve so that its shape can be easily adjusted to avoid obstacles; second, the velocity and acceleration are assigned independently from the path generation so that the inertial terms are controllable. After the path has been generated, a gait algorithm that enables the walking machine to follow the path and maintain stability is developed. Two special cases—straight‐line crab walking and turning about a fixed axis—are studied first. The general case that the walking machine is following an arbitrary curve is then studied. During walking, if the crab angle exceeds a certain limit, the gait needs to be changed in order to maintain stability. The methods for changing the gaits are discussed.
Forward kinematics of a class of parallel (Stewart) platforms with closed‐form solutions
Authors: Zhang Chang‐De , Song Shin‐Min 
Published: July 2007

AbstractThis article studies the geometrical condition for closed‐form solutions of forward kinematics of parallel platforms. It is shown that closed‐form solutions are available if 1 rotational degree of freedom (dof) of the moving platform is decoupled from the other 5 dof. Geometrically, this condition is satisfied when five end‐points at the moving platform (or at the base) are colinear. A general case that these five points do not coincide with each other is studied first and is shown to have 16 possible closed‐form solutions. The variations of parallel platforms that satisfy the above‐mentioned geometrical condition are then discussed. Some of them have the additional feature that the three rotational dof are fully decoupled from the 3 translational dof and their closed‐form solutions are further simplified. One particular case has extremely simple forward kinematics and could be used as an alternative to the Stewart platform.
Compensation of Robot joint variables using special Jacobian matrices
Authors: Mirman C. R. , Gupta K. C. 
Published: July 2007

AbstractIn dealing with an industrial manipulator, the end‐effector accuracy is a major concern. The positioning of the end effector is determined by the controller that utilizes the data from a closed‐form kinematic inversion. The closed‐form inversion uses nominal, i.e., manufacturer specified, values of link lengths, twists, and offsets. Due to manufacturing tolerances, set‐up, and usage, these nominal parameters may be inaccurate. If the nominal parameters contain built‐in error values, the closed‐form kinematic inversion will yield incorrect joint values, and the actual end‐effector position will deviate from its desired position. One may use a parameter identification method to identify the position‐independent error parameter values. This article assumes that this has been done and it presents an iterative compensation algorithm (ICA) through which the identified position‐independent parameter error values may be used to correct the joint values obtained through the closed‐form kinematic inversion. The Denavit and Hartenberg (D‐H) parameters (θsαa) are used to model the givenM‐jointed manipulator, and a set of four special Jacobian matrices (Jθ,Js,Jα, andJa) are formulated. The iterative compensation algorithm allows one to determine theMunknown position‐dependent joint error values by using these four special Jacobian matrices. The improvements obtained through the use of the compensation algorithm will be presented for regular trajectories, as well as when the robot nears certain singularity conditions. Since it is important to know a priori a definite number of iterations that must be performed, the level of compensation after a fixed number of iterations is also studied. Through the presentation of numerous examples, it is shown that the proposed compensation algorithm is simple and straightforward to implement, and it increases the end‐effector accuracy.
Telerobotic manipulator for hazardous environments
Authors: Smith F. M. , Backman D. K. , Jacobsen S. C. 
Published: July 2007

AbstractThe Center for Engineering Design at the University of Utah, in collaboration with Sarcos Research Corporation and others, recently developed the Dextrous Teleoperation System (DTS). The DTS is a master/slave 10 degree of freedom (dof) arm that includes a 3 dof dextrous end effector. The system has demonstrated a number of significant remote manipulation capabilities. This article discusses design considerations, features, and capabilities of the slave Dextrous Arm. An earlier article discussed potential applications, general features, and system capabilities of the DTS. Subsequent articles will discuss the master and control systems.
Supervisory telerobotics testbed for unstructured environments
Authors: Hayati S. , Balaram J. 
Published: July 2007

AbstractThis article describes a telerobotics testbed for performing tasks such as assembly and repair of spacecraft in unstructured environments. This fully operational multiarm system can operate in teleoperated or supervisory control modes, as well as mixed shared‐control modes, thus enabling operations in totally to partially unstructured environments. Various sources of uncertainty are identified and approaches to minimize their effects are presented. In the teleoperated mode, the system uses two force‐reflecting hand controllers to operate two manipulator arms. A third arm is utilized to position four cameras to view the scene. In the supervisory mode, the system can be operated from three different levels: task, process, and servo levels, providing different levels of autonomy and performance. Various tools are provided so that an operator can perform tasks even when objects are partially occluded or their positions are not known a priori. Facilities are available for building models of previously unknown objects on‐line, as well as generating collision‐free motions. Architecturally, the system is designed so that an operator and much of the associated computing environment can be located remotely relative to the robots. As such, ground‐controlled remote manipulation is possible.