bluuebunny/crossref_metadata_2025_split huggingface dataset:
Trajectory Planning for a Mobile Robot
Authors: Steer Barry 
Published: March 2007

Robotics, when successfully carried out, is concerned with artifacts that optimize their own behavior in the light of information using sensors and actuators. The information includes both that which is stored and that which is immedi ately available from the sensors. In this paper the problem addressed is how the speed and the steer angle of a path curvature limited robot-vehicle, one that has to move in order to turn, may be altered in order to achieve desirable changes in its position and orientation. A kinematic description of both a tricycle and "turtle" vehicle architecture is developed. A comparison is made between the two architectures. The effect of modulating the steer angle of a path curvature limited vehicle, a tricycle, with a gaussian envelope is illustrated for various amplitudes of the gaussian and speed of the robot-vehicle. The effect of the time concat enation of the steer angle with two or more gaussian enve lopes shows that a range of activities relevant to the functional needs of a robot-vehicle are possible. A number of other "modulating" functions are identified, and it is suggested that these deserve further investigation.
Force Control in Locomotion of Legged Vehicles over Rigid and Soft Surfaces
Authors: Gorinevsky D.M. , Shneider A. Yu. 
Published: March 2007

The control system of the hexapod walking vehicle, designed at the Institute for Mechanics at Moscow State University and at the Institute for Problems of Information Transmis sion at the USSR Academy of Sciences, is extended to effect the control of foot-contact forces and locomotion in soft soil. The previously developed positional control system enables the computation of commanded motion of the vehicle legs and positional feedback to track this commanded motion. Force feedback is added to the control system, in addition to computation of commanded forces and leg position correc tions for leg sinkage during soft soil locomotion. Such an elaborate control system has made it possible to solve the problems of controlling the distribution of vertical foot force components in locomotion over a rigid surface and of foot-force vectors in locomotion between planes forming a dihedral angle. A number of algorithms are proposed to control vertical force components (loads on legs) and leg sink age in locomotion in elastic and consolidating soils. In the latter case, which corresponds to most natural soils, the bear ing properties of the surface are considered a priori unknown. The results of the experimental implementation of the algorithms are presented.
Buoyancy- and Gravity-Powered Underwater Robots
Authors: Baz A. , Gumusel L. 
Published: March 2007

This paper presents a new concept for driving underwater robots that is based on the interaction between the natural forces of buoyancy and gravity present in the underwater environment. Mathematical models are developed to simulate the static and dynamic characteristics of a single-link arm as in fltcenced by its design parameters and operating conditions. A computer-controlled prototype of the arm is designed, built, and tested to demonstrate the feasibility of the concept. The effect of varying the control gains, sample interval, and con trol law on the dynamic performance of the arm is presented for different payloads. The obtained results suggest the potential of this type of robot in handling objects underwater with minimal external energy.
A Tactile Sensing System for Robotic Manipulation
Authors: Speeter Thomas H. 
Published: March 2007

A tactile sensing system (TSS) for articulated robotic hands is described. The system is composed of flexible touch sensing arrays, access electronics, and algorithms for data sampling and processing. The TSS is meant to exist in a multiprocess ing control environment and is designed to keep low-level procedures such as sensor addressing and data access off of the control system's shared bus. Up to 16 arrays of 256 taxels each can be accessed in parallel with achieved sampling rates of more than 60 Hz. The resolution of the sensors can be dynamically modified by a simple switching technique. This allows very fast sampling rates at low resolution while retain ing the ability to sample with high precision at lower rates. Variance of the resolution changes only the number of taxels and the size of their receptive fields but does not affect the coverage of the array. As part of the discussion about TSS, a generic class of resistive touch sensors is described. These sensors are inex pensive, flexible, and easy to build. Methods for efficient sampling, variable resolution, and shear force detection are introduced, and implementation issues for use with the Utah/ MIT Dextrous Hand are discussed.
An Implementation of a Parallel Algorithm for Real-Time Model- Based Control on a Network of Microprocessors
Authors: Hashimoto Koichi , Ohashi Kenjo , Kimura Hidenori 
Published: March 2007

Model-based trajectory control is a class of advanced manip ulator control strategies that are based on the kinematic and dynamic models of manipulators. Many schemes of model- based control have been proposed; however, most of them are limited within the stage of simulation study and very few have been installed on actual manipulators. The main reason is that the computations required for inverse dynamics are far beyond the ability of the present commercially available microprocessors. In order to achieve real-time high sample- rate control, we have proposed a parallel processing scheme for inverse dynamic computations that is called the resolved Newton-Euler algorithm. It resolves the process for computing the desired torques into subprocesses that have almost com plete concurrency. Because these subprocesses communicate with each other in a regular and local way, they can be di rectly mapped on a distributed processing network system. In this paper, we present a real-time parallel computation architecture for implementing the resolved Newton-Euler algorithm composed of a host personal computer and a net work of microprocessors and transputers. All programs are written in a high-level language, occam. This computation scheme is applied to the trajectory control of the PUMA 560 manipulator. Our controller achieves the sampling period of 0.66 ms.
Probability Distribution of Repeatability of Industrial Robots
Authors: Ramsli Einar 
Published: March 2007

The accuracy with which an industrial robot brings the load to a position and holds it there is perhaps the most important characteristic of an industrial robot. Many researchers have consequently been interested in this field during recent years. A common method for characterizing an industrial robot's ability to return to a position is to use the terms "accuracy" and "repeatability, " where accuracy characterizes the degree to which the actual measured value corresponds to a com manded value and repeatability the closeness of agreement between repeated measured values, under the same condi tions, to the same commanded value (ISO definitions). The normal approximation is regularly used when calculating the repeatability. A test on this assumption for six different industrial robots is reported in this article. Two approaches for this test are used: one looks at the shape of the frequency function for the repeatability figures measured, and the second uses a chi square test on the six data sets. The different tests show that there are small chances that the deviation of an industrial robot will follow a normal distribution. It seems to be a trend that the deviation has longer tails than the normal distribution. Simulation is used to elaborate on the consequences of the invalid assumption of normality in the definition of repeat ability. The conclusion is that it is reasonable to use the normal approximation when there is no strong evidence that the deviation distribution is negatively skewed.
Magnetic Levitation Servo for Flexible Assembly Automation
Authors: Tsuda Masahiro , Higuchi Toshiro , Fujiwara Shigeki 
Published: March 2007

Active magnetic levitation with servo control has the inherent potential to be a friction-free, backlash-free, lubrication-free, and precision multi-degree-of-freedom (DOF) actuator with the capability of multi-axis force sensing. However, magnetic levitation has been conventionally used only for contactless suspension such as magnetic bearings and magnetically levi tated vehicles. This article develops an application of magnetic levitation for actuation and force sensing and calls such a sys tem magnetic levitation servo to distinguish from conventional suspension-only systems. On the other hand, flexible assembly automation is a techni cal and engineering challenge to be accomplished promptly. For this purpose, the authors have developed a Magneti cally end-effector-levitating Instrument for a Skilled-Task- undertaking Expert Robot (MEISTER) by applying magnetic levitation servo. The MEISTER is located between a wrist and an end effec tor in a manipulator to levitate and control the end effector by magnetic forces without any mechanical contact. This friction- free and backlash-free mechanism enables precision control of multi-DOFs and permits the MEISTER to have three versatilely functional properties: (1) programmable compliance: the com pliance and viscous damping of supporting an end effector are magnetically changeable by software; (2) precision multi-DOF actuation: the position and attitude of an end effector can be accurately controlled without friction or backlash by chang ing magnetic forces; and (3) multi-axis force sensing: external forces and moments acting on an end effector can be computed by the MEISTER without any additional sensory equipments from the force equivalent equation. By using these functional properties, the MEISTER can correct a minute misalignment between a couple of mating parts to automate precision inser tion. To investigate the fundamental performance of the MEISTER in experiments, a prototype of a 5-DOF controllable MEISTER is developed. The experiments have shown the following re sults : 1. The MEISTER can be used as an advanced/active Remote Center Compliance (RCC) device. 2. The prototype can quickly position the 5-DOF of a mat ing part with 1-μm resolution. 3. It can measure a five-axis resultant force acting on a part with a resolution of about 0.04N and 0.001 N m. 4. It can successfully perform the RCC assembly method, the ideal RCC method, and the float method in precision insertion operations with the clearance ratio of 0.0004 (where a workpiece has a 20-mm diameter and the clear ance is 8 μm.)
A New Computational Structure For Real-Time Dynamics
Authors: Izaguirre Alberto , Hashimoto Minoru , Paul Richard P. , Hayward Vincent 
Published: March 2007

We present an efficient structure for the computation of robot dynamics in real time. The fundamental characteristic of this structure is the division of the computation into a high-priority synchronous task and low-priority background tasks, possibly sharing the resources of a conventional computing unit based on commercial microprocessors. The background tasks compute the inertial and gravitational coefficients as well as the forces due to the velocities of the joints. In each control sample pe riod, the high-priority synchronous task computes the product of the inertial coefficients by the accelerations of the joints and performs the summation of the torques due to the velocities and gravitational forces. Kircanski et al. (1986) have shown that the bandwidth of the variation of joint angles and of their velocities is an order of magnitude less than the variation of the joint accelerations. This result agrees with the experiments that we have carried out using a PUMA 260 robot. Two main strategies contribute to reduce the computational burden associated with the evaluation of the dynamic equa tions. The first involves the use of efficient algorithms for the evaluation of the equations. The second is aimed at reducing the number of dynamic parameters by identifying beforehand the linear dependencies among these parameters, as well as carrying out a significance analysis of the parameters' contri bution to the final joint torques. We selected an iterative procedure for the computation of the inertial and gravitational coefficients (Featherstone 1984; Renaud 1985; Izaguirre and Paul 1986), and a recursive iter ation for the computation of the velocity torques (Khalil et al. 1986). In our experiments with a PUMA 260, we obtained a set of 52 linearly independent parameters from an initial set of 78 parameters. Identification of the parameters revealed only 23 parameters to be significant. These reductions permit the calculation of the inertias and gravitational coefficients, for the PUMA 260 without load, with 98 multiplications and 70 additions and calculation of the ve lacity torques with 140 multiplications and 110 additions. In the case of an arbitrary load at the end effector, calculation of the inertias and gravitational coefficients requires 190 multi plications and 150 additions and that of the velocity torques, 200 multiplications and 170 additions. Velocity torques, inertial coefficients, and gravitational coefficients can be computed in the background in 20 ms using an Intel 8087 microprocessor. The synchronous task requires only six multiplications and six additions per joint. The actual code used to evaluate this dynamic model is entirely computer generated from experimental data, requiring no other manual intervention than performing a campaign of measurements.
Imperfect Form Tolerancing on Manifold Objects: A Metric Approach
Authors: Boyer M. , Stewart N.F. 
Published: March 2007

In an earlier article we proposed a modeling space for objects defined in terms of tolerances, based on Requicha's ideas on variational classes. To do this, we introduced a certain number of requirements, including the requirements that objects within tolerance should be tamely homeomorphic to the nominal solid and that variational classes should be regular, in the relative topology defined by a certain metric dw and the set of objects tamely homeomorphic to the nominal solid. The practical con sequence of d w-regularity is to exclude variational classes that require all or part of the boundary of an admissible set to be in a fixed or exact position. The subscript in dw is intended to suggest weakness, as the metric in effect introduces a weak condition to be satisfied by the boundary of acceptable r-sets. These ideas led us to the definition of the R-classes, which we claim provides the appropriate definition for a permissible variational class in the context of object tolerancing. In par ticular, we proved that the position, size, and form tolerances ( S, Mp), ( S, Ms), and ( S, M f) are R-classes, at least in the simple case when S is an n-dimensional ball. Generalized ver sions of the regularized Boolean operations, operating not on r-sets but on R -classes, were also introduced; the R-classes are closed under these generalized versions of the regularized Boolean operations. In this article we will extend these results to quite a wide class of position tolerances and present three possibilities for the introduction of a "slow variation constraint. " The latter will be done by means of new metrics d s, which im pose "strong" conditions on the boundary of acceptable sets. Stricter requirements, which ensure slow variation, will be im posed by adding the condition that variational classes be open with respect to these stronger metrics. Finally, it will be shown how the usual "perfect form" approach to tolerancing may be viewed as a special case of the variational class approach by using an appropriately strong slow variation constraint.
A Fully Decentralized Multi-Sensor System For Tracking and Surveillance
Authors: Rao B.S.Y. , Durrant-Whyte H.F. , Sheen J.A. 
Published: March 2007

In many tracking and surveillance systems, multisensor config urations are used to provide a greater breadth of measurement information and also to increase the capability of the system to survive individual sensor failure. Most architectures currently used in such systems rely on having either a central processor where global data fusion takes place or a central communi cations medium through which all messages between sensors must pass. Such centralized architectures give rise to problems with communication and computational bottlenecks and are susceptible to total system failure should the central facility fail. In this article we describe a multisensor surveillance system that achieves a high degree of survivability by employing a decentralized sensing architecture (Durrant-Whyte, Rao, and Hu 1990). Using CCD cameras and optical barriers the system is able to track (in real time) people and robots as they move around a factory room. The decentralized sensing architecture takes the form of a network of Transputer-based sensor nodes, each with its own processing facility, that together do not re quire any central processor, any central communication facility, or any common clock. In this architecture, computation is per formed locally, and communication occurs between any two nodes as and when required. The starting point for the surveillance system is an algo rithm that allows complete decentralization of the multisensor Kalman filter equations among a number of sensing nodes. We develop the algorithm to ensure that internodal commu nication is minimized and can take place without any prior synchronization between nodes. By designing a suitable track management scheme, we are able to extend the system to cope with multitarget tracking. Finally, the specific sensors used in the implementation are interfaced to the algorithm, and the results of the working system are given.
A Reduced-Order Regressor and Its Application to Adaptive Robotic Control
Authors: Stepanenko Yury , Jing Yuan  
Published: March 2007

Manipulator regressors are n x l matrix functions in the dynamic expressions τ = Y(q, q, q)ζr or (1/ D + σ)τ = W(q, q)ζr, which linearize the robot dynamics with respect to a properly defined inertia parameter vector ζr ∈ Rl. Many modern adaptive controllers require on-line computation of a regressor to estimate the unknown inertia parameters and ensure robustness of the closed-loop system. Although the computation ofY(q, q, q) has been studied by Atkeson et al. (1985), Khosla and Kanade (1985), and Khosla (1989), the computation ofW(q, q) for a general n-link robot has not been reported in the literature. This article presents an algorithm to compute W(q, q) for a general n-link robotic manipulator The variables used to construct the regressor matrix are directly available from the outward iteration of a Newton-Euler algorithm; some additional arithmetic operations and first-order, low-pass filtering are needed. The identification of unknown inertia parameters is also discussed.
Identification of Position-Independent Robot Parameter Errors Using Special Jacobian Matrices
Authors: Mirman C.R. , Gupta K.C. 
Published: March 2007

Common production manipulators are designed to be controlled through the use of a closed-form kinematic solution algorithm. This closed-form solution uses manufacturer-specified nomi nal parameter values to model the given manipulator. These position-independent parameters, link lengths, twists, and off sets are geometrical and do not change as the manipulator is driven. However, manufacturing tolerances or usage may cause the actual parameters to deviate from the nominal robot para meters. In some cases, this deviation may be large and thus may cause the closed-form inversion to yield inaccurate joint value results. To assure proper end-effector positioning, it is important to identify these position-independent error values. The identifi cation algorithm to be presented uses the Denavit-Hartenberg (D-H) parameter notation to model any given M-jointed manip ulator. For the given model, a set of special Jacobian matrices are formulated with respect to the four D-H parameters (J θ, Js, Jα, and Ja). This set of four special Jacobian matrices is used to determine a set of D-H error parameter values, which will allow one to estimate the actual D-H parameter values. The iterative regression algorithm for parameter identifi cation uses the end-effector information at several arbitrary manipulator positions, as well as nominal parameter and joint variable information to compute the parameter error values. The use of the special Jacobian matrices allows for easy de termination of mathematical singularity conditions. In addition, statistical methods are employed to provide numerical uni formity between examples and aid in the evaluation process. Through several examples, it will be shown that the use of this parameter identification algorithm produces accurate results. This article will discuss the possibilities of deterministic as well as probabilistic parameter errors. Through the use of this parameter identification algorithm, one is able to identify the D-H parameter error values that will otherwise cause a loss in end-effector accuracy.
Kinematic Dexterity of Robotic Mechanisms
Authors: Park Frank C. , Brockett Roger W. 
Published: March 2007

In this article we develop a mathematical theory for optimizing the kinematic dexterity of robotic mechanisms and obtain a collection of analytical tools for robot design. The performance criteria we consider are workspace volume and dexterity; by the latter we mean the ability to move and apply forces in arbitrary directions as easily as possible. Clearly, dexterity and workspace volume are intrinsic to a mechanism, so that any mathematical formulation of these properties must necessarily be independent of the particular coordinate representation of the kinematics. By regarding the forward kinematics of a mechanism as defining a mapping between Riemannian manifolds, we apply the coordinate-free language of differential geometry to define natural measures of kinematic dexterity and workspace volume. This approach takes into account the geometric and topolog ical structures of the joint and workspaces. We show that the functional associated with harmonic mapping theory provides a natural measure of the kinematic dexterity of a mechan ism. Optimal designs among the basic classes of mechanisms are determined as extrema of this measure. We also examine the qualitative connections between kinematic dexterity and workspace volume.
Robot Grasp Synthesis Algorithms: A Survey
Authors: Shimoga K.B. 
Published: March 2007

This article presents a survey of the existing computational algorithms meant for achieving four important properties in autonomous multifingered robotic hands. The four properties are: dexterity, equilibrium, stability, and dynamic behavior The multifingered robotic hands must be controlled so as to possess these properties and hence be able to autonomously perform complex tasks in a way similar to human hands. Existing algorithms to achieve dexterity primarily involve solving an unconstrained linear programming problem where an objective function can be chosen to represent one or more of the currently known dexterity measures. Algorithms to achieve equilibrium also constitute solving a linear program ming problem wherein the positivity, friction, and joint torque constraints of all fingers are accounted for while optimizing the internal grasping forces. Stability algorithms aim at achiev ing positive definite grasp impedance matrices by solving for the required fingertip impedances. This problem reduces to a nonlinear programming problem. Dynamic behavior algorithms determine fingertip impedances, which, when achieved, lead to a desired dynamic behavior. This problem, too, becomes a linear programming problem. If a robotic hand has to acquire any or all of these proper ties, the corresponding algorithms should become integral parts of the hand control system. These algorithms are collectively referred to in this article as robot grasp synthesis algorithms.