bluuebunny/crossref_metadata_2025 huggingface dataset:
Computer generation of robot dynamics equations and the related issues
Authors: Koplik J. , Leu M. C.
Published: July 2007

Two programs have been developed using the computer algebra system REDUCE to generate the dynamics equations of motion for robot manipulators. One of these programs is based on a Lagrange formulation and the other utilizes a recursive Newton‐Euler formulation. Both programs produce equivalent scalar symbolic expressions for the generalized actuator forces, but the program based on the recursive Newton‐Euler formulation is more efficient for the generation of equations. These programs have been used to generate the dynamics equations of manipulators with as many as six degrees of freedom.

The efficiency of computing forces using the generated scalar symbolic expressions is compared with the efficiency of a numerical algorithm (implemented in FORTRAN '77) based on the recursive Newton‐Euler formulation. Force computation by the method of symbolic equations is shown to be more efficient than the numerical recursive Newton‐Euler algorithm. The technique of symbolic equations is also better adapted to multi‐CPU processing.
Dynamics of manipulation mechanisms with constrained gripper motion. Part I
Authors: Potkonjak Veljko , Vukobratović Miomir
Published: July 2007

This article deals with the dynamics of closed kinematic chains obtained from open ones by introducing some constraints upon the motion of the last segment. Such problems apear very often in practical manipulator operation (writing task, assembling, etc.). The reduced position vector is defined and the dynamic model formed so as to allow the calculation of both the relative motion with respect to the constraint and the reactions, of the constraint. Impact problems are discussed also. Finally, a surface‐type constraint is considered.
Constrained gripper motion in assembly manipulation. Part II
Authors: Vukobratović M. , Potkonjak V.
Published: July 2007

Part II of this article elaborates one practical problem: peg‐in‐hole problem in assembly manipulation. The theory of constrained gripper motion explained in Part I is used to solve the dynamics of the assembly manipulation problem.
Linear multivariable control of two‐link robots
Authors: Seraji H. , Jamshidi M. , Kim Y. T. , Shahinpoor M.
Published: July 2007

Several simple multivariable controllers such as proportional (P), proportional‐derivative (PD), proportional‐integral (PI), and proportional‐integral‐derivative (PID) are investigated and designed for stabilization and regulation of a two‐link planar robot. A new multivariable controller is introduced in this article to achieve command matching. The multivariable controllers are designed on the basis of a linearized model of the robot dynamics. Numerous simulation results are presented to evaluate the performance of the multivariable controllers for the two‐link planar robot.
A servo‐controlled robot gripper with multiple sensors and its logical specification
Authors: Luo Ren C. , Henderson Thomas C.
Published: July 2007

The logical specification of a microprocessor‐based air‐servo‐controlled robot hand is presented, as well as its actual implementation. This hand can accommodate a wide variety of workpieces and allows for flexible assembly through the use of an automatic quick‐change fingertip. The changeable set of gripper fingers is equipped with sensors, including a tactile force sensor, a crossfire sensor, a proximity sensor, and a slip sensor. A changeable set of gripper fingers with different sensing ranges can cope with certain subranges of the workpiece spectrum. A considerable cost saving is achieved by not changing the gripper itself. This specially designed hardware and software system includes position and force feedback. A PUMA 560 is used to test the success of the entire process.
The manipulator language with the characteristic of a functional programming language
Authors: Aramaki Shigeto
Published: July 2007

This article describes the motion‐oriented robot language IML (interactive manipulator language) with the characteristic of a functional programming language. The main functions of IML are (1) It is possible to describe the iterative motions without using a loop. (2) The user‐defined procedures (commands) can be called by specifying the command name. (3) It is possible to describe robot motion (a sequence of the position and orientation of a robot hand) and force magnitude in the task‐oriented Cartesian coordinate system (task coordinate system) suitable for robot tasks. Furthermore, it is possible to describe the translation and rotation of the coordinate system without syntactic distinction. (4) As the teaching data can be easily embedded in the language and can be played back in the force control mode, complex task programming becomes easy. In IML, as the user‐defined command and the teaching data can be used just as the builtin system command; the system can be extended easily and naturally. In this article these features are described, and it is shown that these functions can be realized with the unified representation by introducing the concept of a functional programming language. The effectiveness of IML was confirmed by actually making a robot perform some tasks programmed in IML.
A new displacement sensor using pseudoelastic titanium‐nickel alloy wire
Authors: Takeda Masanori , Hashimoto Minoru , Sato Kimiko
Published: July 2007

The authors have developed a new displacement sensor using a wire of pseudoelastic titaniumnickel (Ti‐Ni) alloy wire. In the measurement, it was found that this alloy exhibited good linearity between the strain and electric resistance. This linearity has been generally applicable up to several percent strain. In addition, a repeat test and dynamic characteristics have been examined. From these results, it is concluded that this Ti‐Ni alloy wire has a possible application as a displacement sensor. Its features include compactness, reduction in weight, and environment attack.
Dynamic simulation of a kinematically redundant manipulator system
Authors: Klein Charles A. , Chirco Antonio I.
Published: July 2007

A number of methods have been proposed for the control of kinematically redundant manipulators, that is, those with more than the minimum number of degrees of freedom. This article uses a dynamic simulation to test whether proposed schemes should, in fact, work well when the dynamics of the actual system are considered. In order to perform a realistic simulation, a nine‐degree‐of‐freedom arm has been designed using commercially available motors. The simulation shows the effects that specifying a secondary goal has on the satisfaction of the primary goal. Also shown is the dependence of servo performance on modeling the load.
Efficient PUMA manipulator jacobian calculation and inversion
Authors: Leahy M. B. , Nugent L. M. , Saridis G. N. , Valavanis K. P.
Published: July 2007

An efficient Jacobian calculation and inversion for a PUMA manipulator permits the real‐time implementation of modern Cartesian space manipulator control techniques. Efficient exact computational formulations for the Jacobian and its inverse have been developed by symbolic reduction techniques. Jacobian computational requirements have been reduced to 66 multiplications and 30 additions. The inverse Jacobian requires only 103 multiplications, 5 divisions, and 70 additions. These computational requirements are easily satisfied in real‐time by modern microprocessor‐based manipulator control systems.
Robot manipulator kinematic compensation using a generalized jacobian formulation
Authors: Driels Morris R. , Pathre Uday S.
Published: July 2007

The kinematic error compensation of robot manipulators is at present being attempted by improving the precision of the nominal robot kinematic parameters. This paper addresses the problem of kinematic compensation using a new mathematical joint model proposed to account for shortcomings in existing methods. The corrected manipulator transformation is formulated in terms of “generalized Jacobians”: relating differential errors at the joints to the differential change in the manipulator transformation. The details of application are discussed for a particular industrial manipulator.
Kinematic modeling of wheeled mobile robots
Authors: Muir Patrick F. , Neuman Charles P.
Published: July 2007

We formulate the kinematic equations of motion of wheeled mobile robots incorporating conventional, omnidirectional, and ball wheels.1 We extend the kinematic modeling of stationary manipulators to accommodate such special characteristics of wheeled mobile robots as multiple closed‐link chains, higher‐pair contact points between a wheel and a surface, and unactuated and unsensed wheel degrees of freedom. We apply the Sheth‐Uicker convention to assign coordinate axes and develop a matrix coordinate transformation algebra to derive the equations of motion. We introduce a wheel Jacobian matrix to relate the motions of each wheel to the motions of the robot. We then combine the individual wheel equations to obtain the composite robot equation of motion. We interpret the properties of the composite robot equation to characterize the mobility of a wheeled mobile robot according to a mobility characterization tree. Similarly, we apply actuation and sensing characterization trees to delineate the robot motions producible by the wheel actuators and discernible by the wheel sensors, respectively. We calculate the sensed forward and actuated inverse solutions and interpret the physical conditions which guarantee their existence. To illustrate the development, we formulate and interpret the kinematic equations of motion of Uranus, a wheeled mobile robot being constructed in the CMU Mobile Robot Laboratory.
Decentralized variable structure control of a two‐arm robotic system
Authors: Özgüner Ü. , Yurkovich S. , Ai‐Abbass F.
Published: July 2007

The control problem for a two‐arm robotic system in coordinated motion is addressed. A hierarchical framework, employing two levels of control hierarchy, is utilized, and the decentralized model reference adaptive control approach using variable structure controllers (DMRA‐VSC) is applied. Within the control hierarchy, the DMRA‐VSC strategy is accomplished at the lower level, where control is responsible for the servoing of each joint. These local controllers are coordinated by the high‐level, central controller, whose task is to provide the local controllers with the upper bound on the dynamical interactions with other subsystems. The local controllers are responsible for making each link follow the prescribed local reference subsystem in moving from one position to another. This is done using the local measurements and the information provided by the central controller. Advantages of the DMRA‐VSC approach for multiple manipulator control include the inherent robustness properties to nonlinearities and interaction effects, the decentralization structure facilitating ease in multiple manipulator system programming and implementation, and the general structure of the controller which allows further extensions such as force feedback.
Object identification using automated decision tree construction approach for robotics applications
Authors: Luo Ren C. , Scherp Ralph S. , Lanzo Mark
Published: July 2007

The objective of this article is to present a novel approach to object recognition and classification for robotic applications using the automated decision tree generation technique. The method developed relies upon simple statistical measurements extracted from object classes and represented in the form of a distance matrix ‘D’ to form a decision tree. The algorithms presented here are computationally efficient and simple to implement. The effectiveness of the features are automatically assessed, allowing for the automatic selection of only those features needed to accomplish object recognition and classification. The performance of the algorithms are successfully tested and demonstrated.
Adaptive force and position control of manipulators
Authors: Seraji H.
Published: July 2007

The article presents simple methods for the design of adaptive force and position controllers for robot manipulators within the hybrid control architecture. The force controller is composed of an adaptive PID feedback controller, an auxiliary signal, and a force feedforward term, and achieves tracking of desired force setpoints in the constraint directions. The position controller consists of adaptive feedback and feedforward controllers as well as an auxiliary signal, and accomplishes tracking of desired position trajectories in the free directions. The controllers are capable of compensating for dynamic cross‐couplings that exist between the position and force control loops in the hybrid control architecture. The adaptive controllers do not require knowledge of the complex dynamic model or parameter values of the manipulator or the environment. The proposed control schemes are computationally fast and suitable for implementation in online control with high sampling rates. The methods are applied to a two‐link manipulator for simultaneous force and position control. Simulation results confirm that the adaptive controllers perform remarkably well under different conditions.
Robot trajectory planning using the convolution operator
Authors: Mirman C. R. , Gupta K. C.
Published: July 2007

An automatic trajectory planning technique is presented to produce smooth joint displacement‐time functions. One can start with few approximately specified joint displacement values, or from a joint displacement‐time function which is not entirely satisfactory. The final joint displacement‐time function passes through the initial and final points, and lies in the vicinity of the intermediate approximate points; it also passes through some points which are in the joint dwell ranges. It is important that the final trajectory exhibit little deviation from the desired displacement values. One would also want to obtain a smooth joint acceleration function, and a rapidly declining envelope for the harmonic spectrum. This new method of trajectory planning is based upon the use of the mathematical operation of convolution. It was found that the use of convolution on a given joint displacement time function tended to decrease the peak acceleration amplitudes, while producing a smooth acceleration function. Convolution also reduced the frequency spectrum amplitudes associated with the joint functions, thus reducing the severity of vibrations which can be induced by the joint motion. While there are some drawbacks to this method, such as increased deviations at intermediate points after convolution, it will be shown that these may be reduced by using techniques described in this article.
Application of discrete‐time model reference adaptive control to a flexible single‐link robot
Authors: Yuh J.
Published: July 2007

This article addresses the feasibility of applying discrete‐time model reference adaptive control techniques to the flexible link of robot mechanisms. The method of separation of variables is used to represent the deflection of the link. A nonlinear model is obtained using a Lagrangian equation, and the candidate frequencies and the associated mode functions are obtained using Bernoulli‐Euler beam theory. By considering the effect of flexibility as an internal disturbance torque acting on the rigid body motion of the system, a discrete‐time MRAC is determined for a single non‐rigid link. The control algorithm is implemented for a collocated sensor and actuator system, and for a noncollocated end‐point sensor and actuator system. Results of computer simulation show the feasibility of this approach and the advantage of using an end‐point sensing system.
Static grip selection for robot‐based automated assembly systems
Authors: Ahmad Shaheen , Feddema John T.
Published: July 2007

In this article we present an algorithmic approach to determine the suitable grasp of an object in an automated assembly environment. The algorithm is based on the available object surfaces and the initial and final task constraints and gripper characteristics. If the imposed task and gripper constraints do not allow a possible grasp, intermediate motions may need to be made to reorient the part. Once a set of possible grasps which statisfy task and gripper constraints are found, the stability of each grasp is analyzed using screw theory. An optimal grasp is one which minimizes the grasping forces over the possible set of grasps. Results utilizing our methodology are presented. Our method can be interfaced with CAD database such as a solid modelling system based on boundary representation for automatic selection of grasping configurations.
Formulation of the kinematic model of a general (6 DOF) robot manipulator using a screw operator
Authors: Payandeh S. , Goldenberg A. A.
Published: July 2007

In general, the manipulator's end‐effector can be located in a desired position and orientation in its work‐space through angular and/or linear displacements of its joints. These joint coordinates can be obtained by solving the loop‐closure equation of the manipulator's kinematic model. The most common method for obtaining this equation is based on the point coordinates 4×4 homogeneous transformation matrix. This method uses a special set of frames which are adapted to the manipulator's configuration. Within the last few years there has been some interest in the use of screw operators (line transformations) to model the kinematic configuration of manipulators and to form the loop‐closure equation. In this article, a kinematic model of a general (6 DOF) manipulator is obtained through the application of a screw operator (dual‐unit quaternion) to represent the screw displacements of the line coordinates of the manipulator link and joint axes. The loop‐closure equation of the closed kinematic chain is obtained by introducing a hypothetical link/joint at the manipulator's end‐effector location. The resultant non‐linear loop‐closure equation is then solved for the joint coordinates using a numerical technique. The method is illustrated with an example.
An extensible ball bar for evaluation of robots' positioning performance
Authors: Vira N. , Lau K.
Published: July 2007

This article describes the development of a one‐dimensional extensible ball bar designed to measure the positioning accuracy and repeatability of industrial robots. The ball bar has a linear travel of 5 cm (2 in) that is monitored by a built‐in electronic transducer having a resolution of 2.5 μm (0.0001 in). At each end of the bar is a precision steel sphere, one of which is attached to an universal joint mounted on a robot's wrist. The other steel ball is magnetically attached to a socket which is firmly located within the work zone of the robot. During the measuring process the robot wrist is programmed to move in an arc whose radius is the nominal length of the bar. The variation of the length of the bar is recorded from the linear transducer and used to obtain a one‐dimensional measurement of the positioning poerformance of the robot. Linear displacement and sag tests indicate that the ball bar has an accuracy of 32 μm (0.0013 in) and a repeatability of 20 μm (0.0008 in). Test procedures to evaluate a robot's performance are also presented.
Tactile array sensor for object identification using complex moments
Authors: Luo Ren C. , Loh Horng‐Hai
Published: July 2007

This article explores object identification by complex moment features obtained using a tactile array sensor. Some complex moment invariants have been derived and implemented eliminating the effects of lateral displacement and rotation from the tactile images. The generation of a decision tree and use of the complex moment features, allow easy identification of object shapes from the tactile array sensor.
Hypersurfaces of special configurations of serial manipulators and related concepts. part III: Measures for the position and orientation space of 6 dof manipulators
Authors: Soylu Resit , Duffy Joseph
Published: July 2007

In this article two alternatives are introduced as measures for the position and orientation space of 6 DOF manipulators which include considerations of joint limitations and scale. The cumulative freedom of the end effector, considered as a rigid body in 3D space, can thus be quantified. These alternative measures are shown to be equivalent for manipulators with spherical wrists. Applications are presented and the new concepts are illustrated by an example.
An experimental investigation of an articulating robotic manipulator with a graphite‐epoxy composite arm
Authors: Choi S. B. , Gandhi M. V. , Thompson B. S. , Lee C. Y.
Published: July 2007

An experimental program was undertaken to investigate the elastodynamic response characteristics of a General Electric P50 robot retrofitted with a prototype graphite‐epoxy forearm. The retrofitted robot with this high‐strength, high‐stiffness lightweight arm was then programmed to execute a variety of maneuvers and the attendant elastodynamic deflections were measured. These experimental data were then compared with the results of complementary studies of the original robot which featured an aluminum arm. The preliminary experimental results from this proof‐of‐concept study clearly demonstrate the superior performance characteristics of the robot retrofitted with the composite arm.
A feasibility study of ic chip wire bond inspection
Authors: Pal A. L. , Patel K. U. , Lai K. K.
Published: July 2007

Product inspection, which is an important step in industrial manufacturing, has depended on human inspectors whose performance is generally inadequate and variable. In the past few years, automated machines for wire bonding have been developed and integrated in the production of quality IC chips for the electronic industry. However, inspection of the wire bonds has not been automated as yet. This article describes a feasibility study for the automated visual inspection of IC chip wire bonds conducted in the Computer Vision Research Laboratory at Arizona State University. Both the system setup and algorithms for detecting some of the typical wire bonding defects such as ball bond, stitch bond placement, and size defects, and connecting wire defects such as missing and shorted wires using two‐dimensional digital images are described.
A miniature robotic boundary layer data acquisition system
Authors: Wilkinson Stuart
Published: July 2007

A sophisticated, highly miniaturized, mobile robot has been developed to collect boundary layer velocity profile data over the surfaces of wind tunnel models. To reduce aerodynamic interference effects the robot was built with dimensions of only 150mm tall X 70mm long X 35mm wide, yet it contained a substantial number of electro‐mechanical and electronic systems for accurately positioning small pressure probes, and for transducing their pressure data. The robot system, which could be controlled in a tele‐operator mode from outside the wind tunnel, was capable of traversing a pressure probe normal to the model surface at two speeds, and was able to stop the probe at any desired location with a positional accuracy of 0.022mm. The robot also included systems that enabled it to move over the model surfaces in a chordwise sense, and to rotate the probe through 180° for use in reversed flow regions. When used operationally during actual wind tunnel testing, the robot functioned flawlessly, and returned high quality boundary layer data.
Redundant robot control using task based performance measures
Authors: Dubey Rajiv , Luh John Y. S.
Published: July 2007

The joint velocities required to move the end‐effector of a redundant robot with a desired linear and angular velocity depend on its configuration. Similarly, the joint torques produced due to the force and moment at the end‐effector also depend on its configuration. When the robot is near a singular configuration, the joint velocities required to attain the end‐effector velocity in certain directions are extremely high. Similarly, in some configurations the joint torque produced at certain joints may be high for a relatively small magnitude of external force. An infinite number of trajectories in the joint space can be used to achieve a desired end‐effector trajectory for redundant robots. However, a joint trajectory resulting in robot configurations requiring lower joint velocities or joint torques is desired. This may be achieved through a proper utilization of redundancy. Local performance measures for redundant robots are defined in this article as indicators of their ability to follow a desired end‐effector trajectory and their ability to apply desired forces at the end‐effector. Thus, these performance measures depend on the task to be performed. Control algorithms which can be efficiently applied to redundant robots to improve these performance measures are presented. These control algorithms are based on the gradient projection method. Gradients of the performance measures used in the control schemes result in simple symbolic expressions for “real world” robots'. Feasibility and effectiveness of these control schemes is demonstrated through the simulation of a seven‐degree‐of‐freedom redundant robot derived from the PUMA geometry.
Dynamic stability analysis of a one‐link force‐controlled flexible manipulator
Authors: Chiou Bing C. , Shahinpoor M.
Published: July 2007

This study analyzes the effects of link flexibility on the dynamic stability of a force‐controlled flexible manipulator. The closed‐loop dynamic equation for a l‐link manipulator is first derived explicitly using the modal representation technique. Stability analysis is then carried out by computing the system eigenvalues. Results show that the link flexibility is one of the causes of dynamic instability of motion of the flexible robotic arm.
Robustness of decentralized robot controller to payload variation
Authors: Stokić D. , Vukobratović M.
Published: July 2007

The decentralized controller for manipulation robot is tested for its robustness to payload variation. First the local controllers are synthesized to withstand variation of inertia round the joints and then the global stability of the robotic system is examined. Three various situations are discussed: a) when actuator inertia is large in comparison to mechanism inertia, b) if the variation of payload is small in comparison to mechanism inertia, and c) if the large variation of payload parameters are expected. An algorithm for testing the robustness of the robot control to parameter variation is established, too. The purpose of the algorithm is to determine the allowable variation of the payload parameters which can be withstood by the simple decentralized controller. On the other hand, by this algorithm the local servosystems can be synthesized which are capable to withstand assumed parameter variation. This synthesis is demonstrated on an example of particular robotic system.
Collision‐avoidance trajectory planning using tube concept: Analysis and simulation
Authors: Suh Suk‐Hwan , Bishop Albert B.
Published: July 2007

The concept of a tube is introduced and is applied to the solving of the collision‐avoidance, minimum‐time trajectory planning problem. A collision‐free space is represented by an articulated tube with parameters of reference points and path tolerances. For obstacle avoidance, the end effector is constrained to move inside of the tube. An algorithm which will find suboptimal solutions for optimizing both path and velocity history of the trajectory by the use of piecewise joint‐space polynomials is presented. This algorithm exploits the robot arm dynamics in realistic environments where obstacles are present and the minimization of task time is desired with smooth motion. Experimental results show that as the path tolerance increases the new algorithm takes advantage of the spatial freedom to provide solutions superior to conventional approaches and to methods based on predefined paths.
Measuring learning progress in intelligent autonomous robots
Authors: Mohamed Ahmed S. , Armstrong William W.
Published: July 2007

AI researchers claim to understand some aspect of human intelligence when their model is able to “emulate” it. In the contexts of mobile robots, the ability to go from teleoperation to autonomy should accordingly be treated not simply as a trick for robotics hackers but as an important epistemological and methodological goal. In this article the experience derived from designing locomotion control systems for both teleoperated and autonomous multi‐legged articulated robots is described.
Completing the forward kinematic calibration of open loop manipulators when single point position sensors are used
Authors: Everett Louis J.
Published: July 2007

Single point sensors can measure the position of one point fixed to a manipulator's end effector. When single point sensors have been used for calibration, it has not been possible to calibrate the orientation of the tool. Furthermore, it can be difficult to calibrate the sensor system. Results in the literature seldom provide a complete kinematic calibration of the manipulator. Presented here is a technique that enables single point sensors to gather sufficient information to complete kinematic calibration. In addition, the method can reduce the burden of calibrating the sensor system.
Distribution of dynamic loads for multiple cooperating robot manipulators
Authors: Walker Ian D. , Marcus Steven I. , Freeman Robert A.
Published: July 2007

For the situation of multiple cooperating manipulators handling a single object, a formulation is presented which allows load distribution of the combined system to be made while taking manipulator dynamics into account. First, object dynamics are used to transform the motion task. An integrated procedure for modeling arm dynamics is detailed. Then a method is introduced which transforms the object load to the joint level. At this level, various methods of load distribution that allow subtask performance are proposed. These methods allow desired object motion while selecting loads desirable to alleviate manipulator dynamic loads.
An integrated programming environment for a generic robotic workcell
Authors: Carayannis G. , Freedman P. , Malowany A.
Published: July 2007

The complexity of modern robotic workcells, consisting of many cooperating elements (e.g., robots, sensing systems) makes programming applications enormously difficult. Even when the application can be easily decomposed into workcelll operations, the tight coupling among these operations due to constraints on precedence and resource sharing makes it difficult to identify and take advantage of possible concurrency. Since robotic workcells are typically configured to repetitively perform an application, we seek to minimize the ‘cycle’ time required, by optimizing the order in which operations take place. Eventually, a sequential program must be written for each workcell element, and they must then execute concurrently. Commercial robot languages and systems provide neither the necessary tools for programming such a distributed collection of elements nor a mechanism for inter‐element communication. In this article the authors propose a two‐part solution to this workcell programming problem: SAGE/WRAP. A graphics interface is provided to the user in order to define the application. Then, from the user's input, SAGE builds a Petri Net description of the workcell application; this is used to obtain a time‐optimal sequence of operations for each workcell element. The time‐optimal sequence then becomes the basis of the runtime program that performs the application. This program is interpreted and executed by the hierarchical workcell runtime environment called WRAP. An example is provided to illustrate the approach.
Hamiltonian description and dynamic control of flexible robots
Authors: Nicosia S. , Tomei P. , Tornambé A.
Published: July 2007

The article is concerned with the problem of modeling and control of flexible robots. This problem is faced by using the Hamiltonian approach and the assumed modes method to obtain an approximate finite dimensional model of the robot dynamics. The pseudo‐linearization method is then applied to design a nonlinear control law that is effective in the neighborhood of the operating points. The article ends with an application to a single‐link robot arm.
Solution schemes for the system equations of flexible robots
Authors: Low K. H.
Published: July 2007

In this work, a method for generating the dynamic equations of flexible robots with open‐chain linkage mechanisms is developed. A general transformation matrix associated with the elastic deformation is introduced. In determining the elastic response, a method of separation of variables and the Galerkin's approach are suggested for the boundary‐value problem with time‐dependent boundary conditions. Besides the formulation scheme, the present work also studies the difficulty of dealing with the inverse kinematic problem, in which the unknowns involve the rigid‐body displacements and the elastic deflections. Finally, the ideas presented here have been implemented in a computer simulation, and the formulation of the boundary‐value problem has been employed to obtain the equations of motion of a flexible robot. Simulation results are presented.
Decentralized adaptive control of robot manipulators
Authors: Oh B. J. , Jamshidi M.
Published: July 2007

A decentralized adaptive control scheme is proposed for the trajectory tracking of a general n‐degree‐of‐freedom robot manipulator. The robot is considered as a set of decoupled second‐order systems with disturbances. The controller consists of feedforward from the desired trajectory based on the “inverse system” of the model, PID feedback from the actual trajectory, and auxiliary input for the compensation of the neglected terms in modeling in each subsystem. The gain is derived in diagonal matrix form, and is adjusted by the model reference adaptive control theory based on the Lyapunov's direct method. The result is high accuracy in path tracking despite the high speed, load change, and sudden torque disturbances. Numerical simulations on.a planar two‐link robot manipulator are presented to show the performance under various practical considerations.
A generalized kinematic modeling method for modular robots
Authors: Benhabib B. , Zak G. , Lipton M. G.
Published: July 2007

Modular robots can be defined as reconfigurable mechanical arms which can be automatically controlled using suitable motion control software. In this article, a generalized kinematic modeling method is presented for such modular robots. This method can be used to derive the individual kinematic models of all the mechanical elements that make up the inventory of modular units, independently of their geometry and sequence of assembly into a robot. A general procedure is also presented to derive a global kinematic model of any robot configured using these modular units. The kinematic modeling technique of the units is based on Denavit‐Hartenberg (D‐H) parameter notation. A provision is also presented for converting “non D‐H” parameter transformations, obtained in assembling the kinematic chain, into D‐H transformations. This D‐H conversion feature allows the modeling technique to preserve its generality when a kinematic model is obtained for the specific robot configuration at hand. The conceptual design of modular robot units that is under development in the Computer Integrated Manufacturing Laboratory (CIML) is also presented to show the feasibility of a modular approach to robot design and to clarify some of the mathematical for mulations developed in the article.
A holdsite method for parts acquisition using a laser rangefinder mounted on a robot wrist
Authors: Roth Gerhard , O'Hara Dave , Levine Martin D.
Published: July 2007

Parts acquisition by a robot is an important industrial problem. Our method makes possible the acquisition of various types of parts which are jumbled together in a pile. An intensity image along with selected range data is used to guide a robot to a location, called a holdsite, at which it can grasp a part. The intensity image gives a rough indication of an area of interest and a laser rangefinder mounted on the robot wrist collects range data in its vicinity. This data is processed using spatial planning methods to find a good holdsite according to safety and stability criteria. The robot is then directed to the holdsite and the part is grasped. The algorithms are simple, fast, and have been successfully tested on a variety of parts.
A local solution with global characteristics for the joint torque optimization of a redundant manipulator
Authors: Nedungadi A. , Kazerouinian K.
Published: July 2007

In this article, a stable local solution with global characteristics is developed for the joint torque optimization problem in redundant robotic manipulators. It is shown that the local optimization of the inertia inverse weighted dynamic torque corresponds to the global kinetic energy minimization problem. The proposed local‐global alternative to the joint torque optimization problem is compared for stability and torque optimality with five different methods used for redundancy resolution of robotic manipulators at the acceleration level. The proposed local‐global solution has been implemented and tested on a planar four‐DOF kinematically redundant lab robot which was designed and built at Southwest Research Institute (SWRI). Several numerical simulations confirm the positive advantages of solutions which have a local as well as a global interpretation. In addition, a “dynamic manipulation index” is introduced to monitor the stability of an optimization problem in a kinematically redundant robot.
Redundancy resolution through local optimization: A review
Authors: Nenchev Dragomir N.
Published: July 2007

Kinematically redundant manipulator arms and other robotic mechanisms provide a means for solving sophisticated motion tasks but require complex research on both mechanical and control problems. So far, many works have been published on kinematic redundancy, however, a systemization is missing. In this article an attempt for such a systemization is presented. It has been limited to methods for redundancy resolution through local optimization. Until now, these methods are most widely used, and it is expected also that they will prevail in the near future. A classification is suggested and the performance capabilities of the methods are discussed and compared. Two reference tables are provided; One of them lists references for different problems on kinematic redundancy as: mechanical design, dexterity measures, multicriteria optimization, global optimization, control design and computational considerations. The other table displays existing publications classified according to the application area of redundant robotic‐mechanisms.
A global approach for the optimal path generation of redundant robot manipulators
Authors: Mayorga R. V. , Wong A. K. C.
Published: July 2007

In this article the optimal path generation of redundant robot manipulators is considered as an optimization problem, with given kinematics and subject to the robot requirements and a singularities avoidance constraint. This problem is formulated as a constrained continuous optimal control problem, which allows to consider joints and velocities constraints and/or manipulator dynamics. This approach is exemplified for a planar redundant manipulator and the resultant state constrained problem is solved by an efficient iterative numerical technique.
An efficient algorithm for finding a collision‐free path among polyhedral obstacles
Authors: Fu Li‐Chen , Liu Dong‐Yueh
Published: July 2007

The use of graph search algorithms on a so called “visibility graph” is a common approach to finding a minimum‐distance collision‐free path among polyhedral obstacles in a 2D environment. Complexity of the search can be greatly reduced by reducing the size of the graph. The focus of this article is to provide an algorithm aimed at constructing asubvisibilitygraph using only “necessary” obstacles, i.e., excluding as many obstacles as possible whose vertices are never via points of the shortest collision‐free path.
Robot arm‐wrist coordination. Part 2. Design guidelines
Authors: Ang Marcelo H. , Tourassis Vassilios D.
Published: July 2007

In the companion article (Part 1), we developed a mathematical framework that provides for the analysis and quantitative rating of arm‐wrist coordination. The objective of this article is to exploit this framework and formulate manipulator design guidelines for effective arm‐wrist coordination and task execution. We explore various arm and wrist designs and quantify their performance in terms of meeting the two design objectives of efficient arm‐wrist coordination and robot flexibility. Numerical simulation experiments highlight the measurable effects of both the fixed manipulator geometry and changing robot configuration on arm‐wrist coordination and demonstrate the impact of the design guidelines on robot performance.
Significance of observation strategy on the design of robot calibration experiments
Authors: Driels Morris R. , Pathre Uday S.
Published: July 2007

This article examines the factors influencing the identification and observability of kinematic parameters during robot calibration. A generalized calibration experiment has been simulated using two different identification techniques. Details of the identification techniques and considerations for implementing them using standard IMSL routines are presented. The factors considered during the simulations include: initial estimates of parameters, measurement accuracy and noise, encoder resolution and uncertainty, selection of measurement configurations, number of measurements, and range of motion of the joints during observations. Results are tabulated for the various cases and suggestions are made for the design of robot calibration experiments.
Behavioral knowledge in sensor/data fusion systems
Authors: Pau L. F.
Published: July 2007

This article proposes a behavioral control formalism to explain situations often encountered in complex sensor/data fusion (eventually decentralized) information acquisition, command and control systems, it involves making the input‐output relations of each actor involved in the fusion process conditional on selected behavioral classes, with error creation and repair options. For each behavioral class, the input‐output relations are modified by concurrent behavioral rules, while the class itself has visible and hidden attributes. A formalism is also given for interactions between actors. This approach allows to describe and analyze such situations as: indirect observations, ambiguous controls, hysterisis, deadlocks, initiation of attention mechanisms. Finally, the engineering use of this approach is illustrated by three concrete designs involving humans operating indoors.
Logical behaviors
Authors: Henderson Thomas C. , Grupen Rod
Published: July 2007

In this article we describe an approach to high‐level multisensor integration organized around certain egocentric behaviors. The task itself determines the sequence of sensing, the sensors used, and the responses to the sensed data. This leads to the encapsulation of robot behavior in terms of logical sensors and logical actuators. A description of this approach is given as well as some examples for dextrous manipulation and mobile robots.
Feature space mapping for sensor fusion
Authors: Flachs G. M. , Jordan J. B. , Beer C. L. , Scott D. R. , Carlson J. J.
Published: July 2007

In the context of a random process scene environment model, a method is presented for fusing data from multiple sensors into a simplified, ordered space for performing electronic vision tasks. The method is based on a new discriminating measure called the tie statistic that is introduced to quantify sensor/feature performance and to provide a mapping from sensor/feature measurement space to a simplified and ordered decision space. The mapping process uses the tie statistic to measure the closeness of an unknown sample probability density function (pdf) to a known pdf for a decision class. Theorems presented in this article relate the tie statistic to minimum probability of error decision making and to the well known Kolmogorov‐Smirnov distance. As examples of the sensor/feature fusion method, the tie mapping process is applied to the object location (cueing) and the texture recognition problems.
Automatic generation of forward and inverse kinematics for a reconfigurable modular manipulator system
Authors: Kelmar Laura , Khosla Pradeep K.
Published: July 2007

Traditional industrial and research manipulators have a fixed configuration and are thus suited for a certain class of tasks. In order to make manipulators flexible and suited for a larger class of tasks we have proposed the concept of a Reconfigurable Modular Manipulator System (RMMS). The RMMS consists of a set of modular links and joints of various sizes; reconfigurable manipulators are designed and built from this system as appropriate for a given task. In order to effectively utilize such a system, one needs algorithms for automatically generating the kinematic descriptions for an arbitrary manipulator configured from the RMMS. Previous research on the kinematics of robotic manipulators has addressed fixed configuration manipulator systems. In this article, we propose an algorithm for automatically generating both the forward and inverse kinematics of a serial linkNdegrees‐of‐freedom reconfigurable manipulator. Generation of the kinematic equations that govern a modular manipulator starts with geometric descriptions of the units, or modules, as well as their sequence in the manipulator. Using this geometric information, we determine the Denavit‐Hartenberg parameters of a reconfigurable manipulator. The Denavit‐Hartenberg kinematic parameters are then used to obtain the forward kinematic transformation of the system. We also address the problem of otaining the inverse kinematics of reconfigurable manipulators. In order to automate the inverse kinematics and to make the procedure as general as possible, we have proposed the idea of scaling a manipulator. We use the efficient numerical approach and in the case of a redundant manipulator, we exploit the extra degrees of freedom to achieve singularity avoidance. We have implemented our algorithms on an Ironies 68020 based single board computer that is used to control the prototype Reconfigurable Modular Manipular System (RMMS) which is being developed in our laboratory.
Solving the inverse kinematics problem via the principle of self‐support
Authors: Novaković Zoran R.
Published: July 2007

A new way of treating various phenomena and processes, called “the principle of selfsupport,” is implemented for solving the inverse kinematics problem. This approach does not use cause/effect philosophy, but is based instead on the concurrency of all kinematic variables involved in the process of executing the desired task. Control action is then seen as a circular and not as a hierarchical process. Such a methodology brings simple numerical algorithms that guarantee stability (tracking). They are realistic from the engineering standpoint and can be implemented using current microprocessor technology. If advanced sensor equipment is available, they appear to be even superior to the analytical solution of the problem.