bluuebunny/crossref_metadata_2025 huggingface dataset:
An algorithm for efficient computation of dynamics of robotic manipulators
Authors: He Xiaogeng , Goldenberg A. A.
Published: July 2007

This article presents a recursive algorithm for computation of dynamics of robot manipulators using the concepts of “augmented body” and “barycenter.” This efficient algorithm is proposed for real‐time control. The proposed method of computation is based on Newton‐Euler formalism, and it can be applied to any rigid‐link manipulator with open‐loop kinematic chains with revolute and/or prismatic joints. The computational efficiency of the proposed method is compared with other published methods.
Optimizing the location of assembly tasks in a manipulator's workspace
Authors: Nelson Brad , Donath Max
Published: July 2007

Off‐line programming of robotic workcells has become an invaluable tool for the workcell designer, however, current robot programming systems lack the capability to automatically determine the locations for performing assembly operations within the manipulator's workspace. A gradient function of manipulability in Cartesian space was developed based on an explicit determination of the manipulability function and the gradient of the manipulability function in joint space. A modified method of the steepest descent optimization procedure was then used as the basis for an algorithm that automatically locates an assembly task away from singularities within a manipulator's workspace. This algorithm can readily be extended to any nonredundant manipulator.
Acceleration and torque feedback for robotic control: Experimental results
Authors: McInroy John E. , Saridis George N.
Published: July 2007

Gross motion control of robotic manipulators typically requires significant on‐line computations to compensate for nonlinear dynamics due to gravity, Coriolis, centripetal, and friction nonlinearities. One controller proposed by Luo and Saridis avoids these computations by feeding back joint acceleration and torque. This study implements the controller on a Puma 600 robotic manipulator. Joint acceleration measurement is obtained by measuring linear accelerations of each joint, and deriving a computationally efficient transformation from the linear measurements to the angular accelerations. Torque feedback is obtained by using the previous torque sent to the joints. The implementation has stability problems on the Puma 600 due to the extremely high gains inherent in the feedback structure. Since these high gains excite frequency modes in the Puma 600, the algorithm is modified to decrease the gain inherent in the feedback structure. The resulting compensator is stable and insensitive to high frequency unmodeled dynamics. Moreover, a second compensator is proposed which uses acceleration and torque feedback, but still allows nonlinear terms to be fed forward. Thus, by feeding the increment in the easily calculated gravity terms forward, improved responses are obtained. Both proposed compensators are implemented, and the real time results are compared to those obtained with the computed torque algorithm.
A multivariable control scheme for robot manipulators
Authors: Tarokh M. , Seraji H.
Published: July 2007

The 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

For 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

Two 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

New 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

This 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

The 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

Traditionally, 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

Remotely 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

The 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

A 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

This 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,

and

determine 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

A 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

A 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

This 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

This 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

The 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

This 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

In 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

The 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

This 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.
Intelligent manipulator system with nonsymmetric and redundant master‐slave
Authors: Sato Katsuhiko , Kimura Motohiko , Abe Akira
Published: July 2007

Some work is so complicated and unsteady that it is not possible to use automatic robots, such as FA robots. In such a case, a teleoperated manipulation system is applied. In this research, the authors aim at a reduction in the operator's physical and mental burdens.

An artificially intelligent manipulator system has been developed with nonsymmetric and redundant master‐slave. This system has five features: (1) a polar coordinates master arm; (2) a highly operational articulated slave arm with 7 degrees of freedom; (3) a nonsymmetric configuration and different degrees of freedom master‐slave control; (4) an expert system; and (5) a new master‐slave control motion, which makes the operator's task easier with automatic force/position control.

The system was experimentally produced and its performance tested and evaluated. A qualitative evaluation was carried out by conducting a comparative test on the conventional master‐slave control and the new master‐slave control. It was found to be effective in reducing operating time, as well as work‐induced fatigue.
Nonlinear ultimate boundedness control and stabilization of a flexible robotic arm
Authors: Nathan P. J. , Singh Sahjendra N.
Published: July 2007

We treat the question of control of an elastic robotic arm of two links. Of course, this approach can be extended to other elastic arms. A nonlinear ultimate boundedness controller (UBC) is synthesized such that in the closed‐loop system the joint angle tracking error is uniformly bounded and tends to a certain small neighborhood of the origin. The controller includes a reference joint angle trajectory generator and integral error feedback. Although the joint angles are controlled using the UBC, elastic modes are excited. A feedback stabilizer is designed for the linearized model including the UBC about the terminal state that is switched only in the vicinity of the equilibrium state for stabilization. Simulation results are presented to show that in the closed‐loop system including the UBC and the stabilizer accurate joint angle trajectory following and elastic mode stabilization are accomplished in the presence of uncertainty.
Accuracy of finite dimensional dynamic models of flexible manipulators for controller design
Authors: Cetinkunt Sabri , Yu Wen‐Lung
Published: July 2007

The dynamics of mechanical systems with distributed flexibility are described by infinite dimensional mathematical models, yet a real controller must be finite dimensional due to the limited bandwidth capabilities of the sensor‐actuator system and real‐time control computer hardware. Therefore, simplified finite dimensional dynamic models must be obtained for the purpose of controller design. This article addresses the issue of selecting the shape and number of mode functions in developing finite order models using a flexible robot arm as an example. The results of this work have consistently shown that the clamped‐free mode shape predicts the closed‐loop system dynamics under a feedback controller much more accurately than pinned‐free mode shapes. However, as the hub inertia increases relative to the flexible beam inertia the difference between the clamped‐free and pinned‐free mode shape model predictions becomes smaller.
Computer generation of symbolic kinematics for robot manipulators
Authors: Mu Eduardo , Cain James T. , Herrera‐Bendezú Luis G.
Published: July 2007

Computer generation of symbolic solutions for the direct and inverse robot kinematics is a desired capability not previously available to robotics engineers. In this article, we present a methodology for the design of a software system capable of solving the direct and inverse kinematics forndegree of freedom (dof) manipulators in symbolic form. The inputs to the system are the Denavit‐Hartenberg parameters of the manipulator. The outputs of the system are the direct and inverse kinematics solutions in symbolic form. The system consists of a symbolic processor to perform matrix and algebraic manipulations and an expert system to solve the class of nonlinear equations involved in the solution of the inverse kinematics problem. The system can be used to study robot kinematics configurations whose inverse kinematics solutions are not known to exist a priori. Two examples are included to illustrate its capabilities. The first example provides explicit analytical solutions, previously believed nonexistent, for a 3 dof manipulator. A second example is included for a robot whose inverse kinematics solution requires intensive algebraic manipulations.
Task‐based configuration control of redundant manipulators
Authors: Seraji Homayoun
Published: July 2007

This article establishes new goals for redundancy resolution based on manipulator dynamics and end‐effector characteristics. These goals can be accomplished by employing the recently developed configuration control approach. Redundancy resolution is achieved by controlling the joint inertia matrix or the end‐effector mass matrix that affect the inertial torques or by reducing the joint torques due to gravity loading and payload. The manipulator mechanical advantage and velocity ratio are also used as performance measures to be improved by proper utilization of redundancy. Furthermore, end‐effector compliance, sensitivity, and impulsive force at impact are introduced as redundancy‐resolution criteria. The new goals for redundancy resolution presented in this article allow a more efficient utilization of the redundant joints based on the desired task requirements. Simple case studies using computer simulations are described for illustration.
An identification method for estimating the inertia parameters of a manipulator
Authors: Lin Shir‐Kuan
Published: July 2007

This article presents an off‐line identification method to estimate the minimal knowledge of the inertia parameters for determining the dynamic model of a manipulator. A new approach is proposed to find a set of the minimal knowledge of the inertia parameters. This set is recursively estimated by moving one joint at a time. The off‐line identification procedure also provides a sufficient condition for a persistently exciting trajectory. A simulation example of Stanford arm illustrates the validity and simplicity of the identification procedure.
Feedback control of robot Arm with discrete nonlinear model
Authors: Tarn T. J. , Bejczy A. K. , Ganguly S.
Published: July 2007

This article looks at the problem of controlling a robot arm from a discrete time perspective. We develop the theories and obtain results that feedback linearizes the discrete nonlinear system representing a PUMA 560 robot arm. The effect of sampling on the performance of the arm has been studied and shown through experiments. The results presented here, where the nonlinear robot model has been linearized and controlled completely in discrete time, are new to the robotics literature. We shown certain restrictions necessary on the sampling time of the system. The results obtained have been experimentally verified at the Center for Robotics and Automation at Washington University. Because a number of researchers have addressed the problem of loss of feedback linearizability under sampling, it was important to develop theories and obtain results in discrete time that take into consideration the effects due to sampling. This problem has been addressed here. Analysis of the control law under the assumptions of bounded input is performed and a recursive sensitivity function is derived. The results we obtain in discrete time show the dependency of the performance of the arm on the sampling time. It has been seen that with a higher sampling frequency the performance of the arm substantially improves and it is expected that close to 1000 Hz sampling rate, the peak performance of the PUMA 560 robot arm, will be reached.
Iterative learning control: A survey and new results
Authors: Moore Kevin L. , Dahleh Mohammed , Bhattacharyya S. P.
Published: July 2007

Learning control is an iterative approach to the problem of improving transient behavior for processes that are repetitive in nature. In this article, we present some results on iterative learning control. A complete review of the literature is given first. Then, a general formulation of the problem is given. Next, we present a complete analysis of the learning control problem for the case of linear, time‐invariant plants and controllers. This analysis offers: (1) insight into the nature of the solution of the learning control problem by deriving sufficient convergence conditions; (2) an approach to learning control for linear systems based on parameter estimation; and (3) an analysis that shows that for finite‐horizon problems it is possible to design a learning control algorithm that converges, with memory, in one step. Finally, a time‐varying learning controller is given for controlling the trajectory of a nonlinear robot manipulator. A brief simulation example is presented to illustrate the effectiveness of this scheme.
Deformation identification and estimation of one‐dimensional objects by vision sensors
Authors: Chen Chichyang , Zheng Yuan F.
Published: July 2007

Using vision sensors to study object deformation is introduced in this article. The vision sensor is used to identify the deformation characteristic and estimate the deformation behavior of flexible beams. First, a nonlinear equation describing the deformation of the beam is given. Then, cubic spline functions are used to approximate the contour of the deformed beam after the beam is detected by the vision sensor. Using the cubic spline approximation and Maclaurin's series expansion, a procedure to determine the deformation characteristic is formulated. To estimate the deformation behavior, numerical differential method to solve the nonlinear equation is used. The error of this numerical method can be controlled with the aid of the vision sensor. Finally, experimental results are given to verify that the proposed methods are effective.
Frequency domain synthesis of trajectory learning controllers for robot manipulators
Authors: Kavli Tom
Published: July 2007

Trajectory learning control is a method for generating near to optimal feedforward control for systems that are controlled along a reference trajectory in repeated cycles. Iterative refinements of a stored feedforward control sequence corresponding to one cycle of the control trajectory is computed based upon the recorded trajectory error from the previous cycle. Several learning operators have been proposed in earlier work, and convergence proofs are developed for certain classes of systems, but no satisfactory method for design and analysis of learning operators under the presence of uncertainties in the system model have been presented. This article presents frequency domain methods for analyzing the convergence properties and performance of the learning controller when the amplitude and phase of the system transfer function is assumed to be within specified windows. Experimental results with an industrial robot manipulator confirm the theoretical results.
Passive ranging using a moving camera
Authors: Shekhar Chandra , Chellappa Rama
Published: July 2007

This article addresses the problem of determining the 3‐dimensional locations of salient points in the environment of a moving camera based on a monocular image sequence obtained by the camera. The camera's translational and rotational velocities are assumed to be known approximately via inertial sensors. The motion of the camera is represented by a constant velocity model. Salient points in the image sequence are extracted using Gabor wavelets and tracked using labeled graph matching. The 3‐D positions of the selected environmental points relative to the camera are then estimated recursively using an extended Kalman filter (EKF), after initialization by two‐frame motion stereo. The motion parameters of the camera are also refined simultaneously. Experimental results on real data are given. © 1992 John Wiley & Sons, Inc.
A systematic method of dynamics for flexible robot manipulators
Authors: Li Chang‐Jin , Sankar T. S.
Published: July 2007

In this article, a systematic method to derive dynamic equations of motion for flexible robot manipulators is developed by using the Lagrangian assumed modes method. The proposed method can be applied to dynamic simulation and control system design for flexible robot manipulators. In the proposed method, the link deflection is described by a truncated modal expansion. The operations of only 3x3 matrices and/or 3 × 1 vectors exist in the method. All the dynamics computations are performed in the link coordinate systems, where the kinematics informations are computed with the forward recursion from the base to the hand tip and the dynamics informations are computed with the return recursion. As generally compared with other existing methods, the method proposed in this article is, computationally, more simple, systematic, and efficient. A computational simulation for a single‐link flexible robot manipulator is presented to verify the proposed method. © 1992 John Wiley & Sons, Inc.
Practical fusion algorithms for rotation matrices: A comparative study
Authors: Zhuang Hanqi , Roth Zvi S. , Sudhakar R.
Published: July 2007

Many computer vision, sensor fusion, and robotic applications require the estimation of a 3 × 3 rotation matrix from a set of measured or computed 3 × 3 noisy rotation matrices. This article classifies solution methods into three categories: nonlinear least squares, linear optimal, and linear suboptimal algorithms. Their performance is compared through simulation studies. It is shown that the linear suboptimal algorithms proposed in this article have an accuracy comparable to that of the optimal algorithms and are about five times faster. Furthermore, a particular nonlinear optimization algorithm is presented that has computational complexity similar to that of the linear optimal procedures. © 1992 John Wiley & Sons, Inc.
Analytic minimum‐norm solution for rate coordination in redundant manipulators
Authors: Varma Hareendra , Huang Ming Z.
Published: July 2007

In this article, we present a novel method that results in efficient minimum norm solution for the rate coordination problem in redundant manipulators. The theory is developed based upon a geometric interpretation that, for minimum norm criterion, vectors orthogonal to constraint space should pass through the origin of the solution space. It is shown that, for any spatial manipulator with 1, 2, or 3 degrees of redundancy, the minimum norm rate solution can be derivedin analytic closed form.An example of the analytic formulation is given for a 3R planar case, substantiated with simulation results. The behavior of this algorithm in nonredundant and near singular situations is also discussed. The method offers an equivalent but much more efficient alternative to using the pseudoinverse in redundancy resolution and, in fact, is applicable to any underdetermined linear system. An alternative formulation of pseudoinverse arrived at in the course of the development is also presented. © 1992 John Wiley & Sons, Inc.
Kinematics of automatic guided vehicles with an inclined steering column and an offset distance: criterion for existence of inverse kinematic solution
Authors: Cheng R. M. H. , Rajagopalan Ramesh
Published: July 2007

This article presents the kinematic model of an automatic guided vehicle (AGV) with an inclined steering column and an offset distance. The vehicle configuration considered here employs the front wheel as the driving and steering wheel. From the kinematic model, a criterion is derived to test the existence of inverse kinematic solution. The criterion is a function of the geometric parameters of the AGV and the steering angle of the wheel. From the criterion defined, conditions for the existence of inverse kinematic solution for steering column configurations with and without inclination and offset distance are obtained. The criterion also presents the range of steering angles for which the inverse kinematic solution exists. The criterion signifies the presence of a unique solution for the motion parameters of the wheel, i.e., the wheel speed, steering angle, and steering rate for desired values of the motion parameters of the AGV, i.e., the linear and angular velocities of the AGV. This information is needed for the guidance control of AGVs based upon a kinematic control scheme (dead‐reckoning control) without using the absolute position referencing system to follow a predefined path at prescribed linear and angular velocities. © 1992 John Wiley & Sons, Inc.
Explicit dynamic equations for a chain of flexible links
Authors: Deng Zhongping , Wang Liping
Published: July 2007

A D'Alembert‐Lagrangian approach is developed for the dynamics of a chain of flexible links. The governing equations and boundary conditions for each link are derived. While the approach is developed for chains with any numbers of links, the dynamic equations are written explicitly for a chain with two flexible links and a payload. © 1992 John Wiley & Sons, Inc.
Objects interaction using superquadrics for telemanipulation system simulation
Authors: Agba Emmanuel I. , Wong Tin‐Lup , Huang Ming Z. , Clark Andrew M.
Published: July 2007

A high‐fidelity “hybrid” telerobotic simulator suitable for telemanipulation rehearsal, supervisory control, operator training, and human factors performance evaluation has been developed. The simulator is capable of operation in the conventional rate‐control, master/slave control, and a data‐driven preprogrammed mode of operation. It has teach/playback capability, which allows an operator to generate joint commands for real‐time teleoperation. For high‐level task execution, the operator selects a specific task from a set of menu options and the simulator automatically generates the required joint commands. In this article, an object detection strategy that has been implemented in the simulator for more realistic telemanipulation is presented. The object detection technique is based on the use of superellipsoids, which have a convenient inside‐outside function for interference testing. The technique, which treats both moving and stationary objects in a consistent manner, has proved to be easy to implement and optimize for real‐time applications. The object detection feature is also used to provide visual feedback as a low‐cost force reflection strategy.
Variable structure trajectory control of an elastic robotic arm
Authors: Madhavan Sethu K. , Singh Sahjendra N.
Published: July 2007

This article introduces a variable structure system scheme to control the end effector trajectory of a two‐link flexible robotic arm. Because control of the actual tip position leads to unstable zero dynamics, control of points in the neighborhood of the tip is considered. An output is chosen as the sum of the joint angle and tip elastic deformation times a constant factor for each link. For the chosen output, a discontinuous output control law is derived based on the variable structure theory. The control law thus derived accomplishes the desired trajectory tracking of the output. A linear stabilizer is designed using the pole assignment technique for the final capture of the terminal state and stabilization of the elastic modes. Simulation results are presented to show that in the closed‐loop system large maneuvers can be performed in the presence of payload uncertainty, thereby exhibiting the robustness of the controller.
A preliminary experiment in dual‐channel tactile information flow
Authors: Taylor R. M. , Kawarizadeh B. , Hemami H. , Boyer K. L.
Published: July 2007

Recent developments in theoretical robotics, sensor technology and fusion, and on‐line processing allow for both anthropomorphic behavior on the part of robots, as well as tactile and environmental intelligence. This article considers the feasibility, use, and applications of dual‐channel tactile information flow. In single‐channel systems, the tactile sensors are exclusively mounted on the robot, whereas in dual‐channel systems both the robot and the environment with which it interacts are supplied with sensors. A test bed is described by which a number of single‐ and dual‐channel experiments are carried out. The focus of the dual channel experiments is on its use as this additional channel of sensory perception and on its potential for application in future robotic systems.
Joint trajectory generation for redundant robots in an environment with obstacles
Authors: Guo Z. Y. , Hsia T. C.
Published: July 2007

Collision avoidance is an absolutely essential requirement for a robot to complete a task in an environment with obstacles. For kinematically redundant robots, collision avoidance can be achieved by making full use of the redundancy. In this article, the problem of determining collision‐free joint space trajectories for redundant robots in an environment with multiple obstacles is considered, and the “command generator” approach is employed to generate such trajectories. In this approach, a nondifferentiable distance objective function is defined and is guaranteed to increase wherever possible along the trajectory through a vector inN(J), the null space of Jacobian matrixJ.Algorithms that implement this nondifferentiable optimization problem are fully developed. It is shown that the proposed collision‐free trajectory generation scheme is efficient and practical. Extensive simulation results of a four‐link robot example are presented and analyzed.