bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experiments Toward On-Line Identification and Control of a Very Flexible One-Link Manipulator
Authors: Rovner Daniel M. , Cannon Robert H. 
Published: March 2007

An adaptive control algorithm based on the self-tuning regu lator concept has been experimentally investigated for appli cation to a very flexible one-link robotic manipulator. Adap tive control is an attractive methodology for maintaining the performance of precise controllers designed for such manipu lators under conditions of varying end-effector load. The use of noncollocated sensors and actuators to give good accuracy in tip positioning also places stringent requirements on the accuracy of dynamic models used for controller design. Identification and control design techniques suitable for on-line implementation have been demonstrated experimen tally on such a single-link flexible manipulator. The identifi cation algorithm employed is a filtered version of the recur sive least-squares algorithm. It is a development of algorithms previously used with the Stanford four-disk sys tem. Stable controllers with good step responses were de signed using the system models identified with the identifica tion algorithm. The necessity of filtering sensor data to achieve accurate identification was motivated analytically and confirmed experimentally. Accurate identification of 2 system transfer functions was achieved with a 4-s-long data record. The algorithms demonstrated could be used in an adaptive-learning setting to improve the performance of a ro botic system subject to varying loads.
A Three-Wheeled Self-Adjusting Vehicle in a Pipe, FERRET-1
Authors: Okada Tokuji , Kanade Takeo 
Published: March 2007

This paper describes three-wheeled vehicles that can move inside a pipe and adjust to the shape and size of the pipe. We propose two types of vehicles: tractive and nontractive. Both types are based on two hinged arms. The tractive vehicle has a driving wheel at a hinge and two sphere bearings at the ends of the arms. The driving wheel rotates about the axis perpendicular to the plane in which the two arms move. The wheel can freely move sideways. The sphere bearings can move in all directions like ball casters. Since the stretch force of the arm to the pipe wall is generated mechanically by pulleys and a spring, the vehicle rests in the pipe by pressing the two arms in opposite directions where the diameter is the biggest and it moves according to the action of the driving wheel. Three wheels of the nontractive vehicle are sphere bearings. We analyze the shape geometry of the pipe to obtain sta bility conditions under which the vehicle can move, and we consider friction and gravity bringing the vehicle to rest in the pipe. We also analyze the kinematics and dynamics of lo comotion, and we simulate locomotion of the vehicle in the plane in which the biggest diameter of the pipe is measured. The results of the simulation prove the self-adjustability of the vehicle to the shape and size of the pipe. Experimental results show that the vehicle can move and self-adjust in an inclined or twisted pipe with a deep angle.
Multisensor Knowledge Systems
Authors: Henderson T. , Weitz E. , Hansen C. , Mitiche A. 
Published: March 2007

We describe an approach which facilitates and makes explicit the organization of the knowledge necessary to map multi sensor system requirements onto an appropriate assembly of algorithms, processors, sensors, and actuators. We have previously introduced the multisensor kernel system and logi cal sensor specifications as a means for high-level specifi cation of multisensor systems. The main goals of such a characterization are to develop a coherent treatment of multi sensor information, to allow system reconfiguration for both fault tolerance and dynamic response to environmental con ditions, and to permit the explicit description of control. In this paper we show how logical sensors can be incorpo rated into an object-based approach for the interpretation of 3D structure. Considering the inherent difficulties in inter preting general configurations of lines in space, and consider ing the ubiquitousness of special line configurations in manu factured environments and objects, we advocate the use of computational units tuned to the occurrence of special config urations. The organized use of these units circumvents the inherent difficulties in interpreting general configurations of lines. After a brief examination of the problem of interpreting general configurations of lines in space, a number of compu tational units are proposed which are naturally derived from angular relations. The process of propagation (which allows interpretation to spread over the image) is also advocated. Such computational units and processes, which are simple and efficient, can be conveniently organized in a rule-based framework where the occurrence of the various special config urations can be tested. The multisensor knowledge system provides such a framework.
Uncertainty and Compliance of Robot Manipulators with Applications to Task Feasibility
Authors: Pai Dinesh K. , Leu M.C. 
Published: March 2007

The uncertainty and compliance of a robot manipulator used to perform a task are considered. A formula is derived for the efficient computation of a tight bound on the uncertainty of the end effector, given the uncertainty in the kinematic pa rameters of the robot. It is shown that the total uncertainty is the Minkowski difference of the manipulator uncertainty and the task position uncertainty. Simulations are performed in which the results are used to determine configurations of a robot for which the total uncertainty is within a specified tolerance. The suitability of the compliance of a manipulator for performing a planar peg-in-hole type assembly task is also studied. Manipulators are modeled as having rigid links and compliant joints, following experimental results. It is shown that given any symmetric positive semidefinite compliance, a robot manipulator of the above type can be constructed that will realize this compliance at some point in its work space. A new condition on the stiffness is proposed for preventing jamming. If the peg is supported by the end effector of a robot, we can determine configurations of the robot at which jam ming can be avoided. Simulations are performed to compute the no-jam configurations of a manipulator. The results developed here have direct application to sev eral areas of robotics: determining whether a robotic task is feasible in the presence of uncertainty and joint compliance, choosing work space locations for a robotic task, and the design and selection of robot manipulators. 1. This is called two- point contact in Whitney (1982). 2. That is, errors resulting from both the end-effector and task position uncertainties. 3. The symbol ( ) T denotes the transpose. 4. The half-size of a box is half the length of the box in a specified coordinate direction. 5. Also called the set-sum. 6. The effective compliance refers to the compliance at the peg tip resulting from the compliance of the robot or some other support.
Ability of a Robot to Travel Through its Free Work Space in an Environment with Obstacles
Authors: Wenger Philippe , Chedmail Patrick 
Published: March 2007

This article presents a new geometric analysis of the free work space of a robot among obstacles. The free work space (FW) is defined as the set of positions and orientations that the robot's end effector can reach, according to the joint limits and the various obstacles lying in the environment. The aim is to give global descriptions of the robot's ability to move in the operational space (which coincides with Carte sian space when only position coordinates are specified). The main contribution of this work is the characterization of the effects of obstacles on the work space geometry, as well as on its topology. The ability of a robot to move freely in its work space (called the "moveability") is difficult to describe and needs stringent formalizations. The concept of move ability is introduced through various properties and their cor responding necessary and sufficient conditions. Using a Con structive Solid Geometry (CSG) Computer-Aided Design (CAD) description of robots and obstacles and an octree model of the FW, these properties permit characterization of selected moveability areas in the FW, where, for instance, any n points can be linked together or where any continuous trajectory can be achieved without changing configuration. This new global description is of great interest for the user of CAD systems when designing robotic cells.
Analysis of Swept Volume via Lie Groups and Differential Equations
Authors: Blackmore Denis , Leu M.C. 
Published: March 2007

The development of useful mathematical techniques for an alyzing swept volumes, together with efficient means of im plementing these methods to produce serviceable models, has important applications to numerically controlled (NC) machin ing, robotics, and motion planning, as well as other areas of automation. In this article a novel approach to swept volumes is delineated—one that fully exploits the intrinsic geometric and group theoretical structure of Euclidean motions in or der to formulate the problem in the context of Lie groups and differential equations. Precise definitions of sweep and swept volume are given that lead naturally to an associated ordinary differential equation. This sweep differential equation is then shown to be related to the Lie group structure of Euclidean motions and to generate trajectories that completely determine the geometry of swept volumes. It is demonstrated that the notion of a sweep differential equation leads to criteria that provide useful insights concern ing the geometric and topologic features of swept volumes. Several new results characterizing swept volumes are obtained. For example, a number of simple properties that guarantee that the swept volume is a Cartesian product of elementary mani folds are identified. The criteria obtained may be readily tested with the aid of a computer.
Restricted Jacobian Matrices of Redundant Manipulators in Constrained Motion Tasks
Authors: Nenchev Dragomir N. 
Published: March 2007

Kinematically redundant manipulators are considered, with a prespecified end-effector task and multiple additional tasks. The number of additional tasks is assumed to be equal to or less than the degree of redundancy. This assumption justifies an equal-priority (or duality) concept for the end-effector task and additional tasks. Based on this concept, expressions for two restricted Jacobian matrices are derived: the restricted manipulator Jacobian and the restricted additional-task Jaco bian. It is shown that generalized inverses of these matrices can be utilized to derive two alternative solutions of instanta neous inverse kinematics that satisfy both tasks simultaneously. The first solution, which is based on the null space of the manipulator Jacobian, has been widely applied in various redundancy-resolution techniques; it is shown that when used in manipulator self-motion tasks, this solution yields cyclic- path motion in joint space. The second solution utilizes the null space of the additional-task Jacobian; it is dual to the first one. Hence, in the particular case of end-effector motion with additional-task maintenance, this solution yields cyclic-path motion as well. It is further shown that at algorithmic singularities, both restricted Jacobian matrices lose rank simultaneously. Algo rithmic singularities, together with the well-known manipulator singularities, and newly defined additional-task singularities are shown to play an important role in kinematic analysis. The duality concept calls for the definition of a new type of dexterity measure: the additional-task performance measure. The restricted Jacobian matrices are shown to also provide a convenient tool for deriving "restricted" dexterity measures that are directly related to the various types of singularities. Typical end-effector/additional-task combinations have been tested through computer simulation, illustrating the application of the restricted Jacobian matrices to configuration analy sis and path-planning problems of redundant manipulators in constrained-motion tasks.
Toward a Robot Architecture Integrating Cooperation between Mobile Robots: Application to Indoor Environment
Authors: Noreils Fabrice R. 
Published: March 2007

This article describes an architecture for cooperative and au tonomous mobile robots. The architecture is composed of three levels: functional, control, and planner levels. The functional and control levels manage robot resources, while the planner level carries out complex operations such as planning and cooperation. The cooperation is composed of two phases: (1) collabora tion, in which a task is decomposed into subtasks and subtasks are allocated through a set of robots; and (2) coordination, in which robots actually coordinate their activities to fulfill the initial task using the notion of coordinated protocols. Moreover, a language has been developed to program the coordination. This architecture exhibits important benefits such as (1) mod ularity (the robot can work autonomously or within a team), (2) robustness (although some modules on the robot fail, it is still able to perform useful tasks), and (3) programmability. Two actual examples using two indoor mobile robots are described to demonstrate the interest of this approach.
Experimental Object- Level Strategic Control With Cooperating Manipulators
Authors: Schneider Stanley A. , Cannon Robert H. 
Published: March 2007

This article presents the high-level control module and user interface of the Dynamic and Strategic Control of Cooperating Manipulators (DASCCOM) project at Stanford University's Aerospace Robotics Laboratory. In addition to cooperative dynamic control, DASCCOM incorporates real-time vision- based feedback, a novel strategic programming technique, and an iconic "object-only" graphical user interface. By focusing on the vertical integration problem, we are examining not only these subsystems, but also their interfaces and interactions. The control system implements a multilevel hierarchical structure interconnected via a real-time network. At the highest level, a mouse-driven graphical user interface allows an opera tor to direct the activities of the system conceptually. Strategic command is provided by an event-driven finite state machine. This methodology provides a powerful yet flexible technique for managing concurrent system interactions. The dynamic controller implements object impedance control —an extension of Neville Hogan's impedance control concept to cooperative multiple-arm manipulation of a single object. This article concentrates on user interfacing techniques and strategic programming capabilities. These modules allow the user to directly specify conceptual object relationships. Experimental results are presented, showing the system lo cating and identifying a moving object, "catching" it, and performing a simple cooperative assembly. Each of these operations is executed autonomously, with only object-level task-specification direction from a remote operator.
Shape from Diameter
Authors: Rao Anil S. , Goldberg Kenneth Y. 
Published: March 2007

Our objective is to automatically recognize parts in a struc tured environment (such as a factory) using inexpensive and widely available hardware. In this article we consider the pla nar problem of determining the convex shape of a polygonal part from a sequence of projections. Projecting the part onto an axis in the plane of the part produces a scalar measure, the diameter, which is a function of the angle of projection. The diameter of a part at a particular angle can be measured using an instrumented parallel-jaw gripper. First, we present the negative result that shape cannot be uniquely recovered: for a given set of diameter measurements, there is an (uncountably) infinite set of polygonal shapes con sistent with these measurements. Because most of these shapes have parallel edges of varying lengths, we consider the related problem of identifying a representative polygon with no par allel edges. We show that, given a diameter function, deciding whether such a polygon exists is NP-complete. These results motivate us to consider the problem of recog nizing a part from a known (finite) set of parts. Given a set of polygonal parts with a total of N faces, can we find the short est sensing plan for disambiguating the parts? Only diameters at n ≤ N stable faces can be measured. We construct an in ternal representation of these stable diameters in O(N + n 3) time and then give two planning algorithms: one constructs an optimal sensing plan in time O( n42 n), the other constructs a suboptimal sensing plan in time O( n2 log n). Neither plan requires more than n measurements.
Real-Time Visual Servoing Using Controlled Illumination
Authors: Urban J.P. , Motyl G. , Gallice J. 
Published: March 2007

A real-time visual servoing approach is applied to robotics tasks consisting of the positioning of the end effector with respect to a priori known polyhedral objects. The vision appa ratus is constituted by a compact CCD camera rigidly coupled with two laser stripes mounted on the wrist of a robot ma nipulator. The objective is to servo the robot end effector at a constant position and orientation with respect to a known object in three-dimensional space in the field of view of the sensory system. The approach is expressed in terms of sensor-based control (Samson et al. 1991) applied to visual servoing (Chaumette 1990; Urban 1990). In the case of camera—light stripe coupling, the elementary visual signals used for visual servoing are the points of discontinuity in the light stripes. The feasibility of the approach is demonstrated in a factory automa tion task consisting of the positioning of the end-effector tool over a vehicle battery. Both simulation and experimentation results are presented, proving the robustness and stability of the algorithm.
A Group Theoretic Formalization of Surface Contact
Authors: Yanxi Liu  , Popplestone Robin 
Published: March 2007

The surface contacts between solids are always associated with a set of symmetries of the contacting surfaces. These symmetries form a group known as the symmetry group of the surface. In this article we develop a group theoretic formalization for describing surface contact between solids. In particular we define (1) primitive and compound features of a solid, (2) a topological characterization of these features, and (3) the symmetry groups of primitive and compound features. The symmetry group of a feature is a descriptor of the fea ture that is at once abstract and quantitative. We show how to use group theory concepts to describe the exact relative motion (position) of solids under surface contacts, which can be either rigid or articulated. The central result of this article is to prove the following: 1. When primitive features of a solid are mutually dis tinct, 1-congruent or 2-congruent, the symmetry group of a compound feature can be expressed in terms of the intersection of the symmetry groups of its primitive features. 2. When two solids have surface contact, their rela tive positions can be expressed as a coset of their common symmetry group, which in turn can be ex pressed in terms of the intersections of the symmetry groups of the primitive features involved in this con tact. These results show that using group theory to formalize surface contacts is a general approach for specifying spatial relationships and forms a sound basis for the automation of robotic task planning. One advantage of this formulation is its ability to express continuous motions between two surface- contacting solids in a computational manner and to avoid combinatorics arising from multiple relationships, especially from discrete symmetries in the assembly parts and their fea tures. At the end of this article, a geometric representation for symmetry groups and an efficient group intersection algorithm using characteristic invariants are described.
Discrete-Time Model Reference Adaptive Controller Designs for Robotic Manipulators
Authors: Yang Shiaw-Pyng , Woo Peng-Yung , Wang Rongdong 
Published: March 2007

On-line computer control with high speed and accuracy is needed in industrial robotics. Thus, discrete-time controller design for robotic manipulators is necessary. In this article, the two continuous-time model reference adaptive control schemes presented in Yang and Woo (1992) are put forth in discrete forms. The stability analysis stems from Lyapunov's Direct Method (Slotine and Li 1991), which guarantees the asymptotic stability of a system. Like any discrete-time control system, the time required for the computer to perform the necessary computation may result in extended sampling time, which could degrade the stability of the system. In this article, we obtain the sufficient condition of stability for the designed discrete-time controllers. A set of right sampling time and weighting factors are chosen to show the highly accurate tracking. Through the MATLAB software (PC MATLAB MANUAL 1992) simulation, we can see that the manipulator does follow the desired trajectory with high accuracy, even when the payload is changing. It proves the effectiveness of the designed controllers.
Soft Robotic Fingertips
Authors: Shimoga K.B. , Goldenberg A.A. 
Published: March 2007

Three potential problems exist in multifingered robotic hands. First, the impact forces that result during each instant of grasping a rigid object can affect the functioning of the fingertip sensors. Second, a hand with hard fingers cannot securely grasp objects that have uneven surfaces due to the poor conformability of the fingers. Third, repetitive strains are induced into the fingers throughout a manipulation task. If they are not dissipated, the manipulation becomes jerky, the func tioning of the fingertip sensors is affected, and the life of the finger's skeletal structure may become short. In this work, six fingertips constructed from plastic, rub ber, sponge, fine powder, paste, and gel are experimentally compared for their ability to overcome the above problems. Results show that the sponge fingertip is the most suitable and the plastic fingertip the least suitable for our application. For practical reasons, however, gel is preferred over sponge. In view of these results, it is recommended that future robotic hands employ soft fingers, or at least fingers with soft tips, constructed out of carefully chosen materials.
Soft Robotic Fingertips
Authors: Shimoga K.B. , Goldenberg A.A. 
Published: March 2007

Part I of this article showed that making robotic fingers from soft materials helps them cope with the following three prob lems. First, the impact forces that occur at the instant of grasping are reduced. Second, commonly used objects with uneven surfaces can be grasped comfortably due to the confor mal nature of the soft fingers. Third, the repeated strains that are induced during manipulations are dissipated. The problem to solve now is that of modeling and controlling the overall impedance of a soft finger or of a finger that has a soft tip. This is the issue addressed in this part. This part presents the experimental determination of the pas sive impedance parameters of a soft (gel-filled) fingertip and formulates an approach to account for the soft fingertip model when controlling the overall impedance of a finger that carries the soft tip. The approach is demonstrated via four experi ments, each with a unique goal. Also showed experimentally is how the presence of passive damping helps reduce the peak impact forces that occur as a rigid object is grasped by the fingers of a robotic hand.