bluuebunny/crossref_metadata_2025 huggingface dataset:
On Path Planning and Obstacle Avoidance for Nonholonomic Platforms with Manipulators: A Polynomial Approach
Authors: Papadopoulos Evangelos , Poulakakis Ioannis , Papadimitriou Iakovos
Published: July 2003

A planning methodology for nonholonomic mobile platforms with manipulators in the presence of obstacles is developed that employs smooth and continuous functions such as polynomials. The method yields admissible input trajectories that drive both the manipulator and the platform to a desired configuration and is based on mapping the nonholonomic constraint to a space where it can be satisfied trivially. In addition, the method allows for direct control over the platform orientation. Cartesian space obstacles are also mapped into this space in which they can be avoided by increasing the order of the polynomials employed in planning trajectories. The additional parameters required are computed systematically, while the computational burden increases linearly with the number of obstacles and the system elements taken into account. Illustrative examples demonstrate the planning methodology in obstacle-free and obstructed environments.
Time Optimal Trajectories for Bounded Velocity Differential Drive Vehicles
Authors: Balkcom Devin J. , Mason Matthew T.
Published: July 2003

This paper presents the time optimal trajectories for differential drive vehicles in the unobstructed plane. The wheel angular velocities are bounded, but may be discontinuous. The paper proves the existence of optimal controls, derives the structure of optimal trajectories, and develops an algorithm for producing a time optimal trajectory between any two configurations. Every nontrivial optimal trajectory is composed of straight segments alternating with turns about the robot's center. Optimal trajectories may have as many as five actions, but four actions are sufficient—for every optimal trajectory of five actions, there is an equally fast trajectory with four actions.
Robust Geometric Computing in Motion
Authors: Halperin Dan
Published: July 2003

Transforming a geometric algorithm into an effective computer program is a difficult task. This transformation is particularly made hard by the basic assumptions of most theoretical geometric algorithms concerning complexity measures and (more crucially) the handling of robustness issues, namely issues related to arithmetic precision and degenerate input. The paper starts with a discussion of the gap between the theory and practice of geometric algorithms, together with a brief review of existing solutions to some of the problems that this dichotomy brings about.

We then turn to an overview of the CGAL project and library. The CGAL project is a joint effort by a number of research groups in Europe and Israel to produce a robust software library of geometric algorithms and data structures. The library is now available for use with significant functionality. We describe the main goals and results of the project.

The central part of the paper is devoted to arrangements (i.e., space subdivisions induced by geometric objects) and motion planning. We concentrate on the maps and arrangements part of the CGAL library. Then we describe two packages developed on top of CGAL for constructing robust geometric primitives for motion algorithms.
Randomized Kinodynamic Motion Planning with Moving Obstacles
Authors: Hsu David , Kindel Robert , Latombe Jean-Claude , Rock Stephen
Published: July 2003

This paper presents a novel randomized motion planner for robots that must achieve a specified goal under kinematic and/or dynamic motion constraints while avoiding collision with moving obstacles with known trajectories. The planner encodes the motion constraints on the robot with a control system and samples the robot's state × time space by picking control inputs at random and integrating its equations of motion. The result is a probabilistic roadmap of sampled state × time points, called milestones, connected by short admissible trajectories. The planner does not precompute the roadmap; instead, for each planning query, it generates a new roadmap to connect an initial and a goal state× time point. The paper presents a detailed analysis of the planner's convergence rate. It shows that, if the state× time space satisfies a geometric property called expansiveness, then a slightly idealized version of our implemented planner is guaranteed to find a trajectory when one exists, with probability quickly converging to 1, as the number of milestones increases. Our planner was tested extensively not only in simulated environments, but also on a real robot. In the latter case, a vision module estimates obstacle motions just before planning starts. The planner is then allocated a small, fixed amount of time to compute a trajectory. If a change in the expected motion of the obstacles is detected while the robot executes the planned trajectory, the planner recomputes a trajectory on the fly. Experiments on the real robot led to several extensions of the planner in order to deal with time delays and uncertainties that are inherent to an integrated robotic system interacting with the physical world.
Phase Regulation of Decentralized Cyclic Robotic Systems
Authors: Klavins E. , Koditschek D.E.
Published: July 2003

We address the problem of coupling cyclic robotic tasks to produce a specified coordinated behavior. Such coordination tasks are common in robotics, appearing in applications like walking, hopping, running, juggling and factory automation. In this paper we introduce a general methodology for designing controllers for such settings. We introduce a class of dynamical systems defined over n -dimensional tori (the cross product of n oscillator phases) that serve as reference fields for the specified task. These dynamical systems represent the ideal flow and phase couplings of the various cyclic tasks to be coordinated. In particular, given a specification of the desired connections between oscillating subsystems, we synthesize an appropriate reference field and show how to determine whether the specification is realized by the field. In the simplest case that the oscillating components admit a continuous control authority, they are made to track the phases of the corresponding components of the reference field. We further demonstrate that reference fields can be applied to the control of intermittent contact systems, specifically to the task of juggling balls with a paddle and to the task of synchronizing hopping robots.
Manipulation of Pose Distributions
Authors: Moll Mark , Erdmann Michael A.
Published: July 2003

For assembly tasks parts often have to be oriented before they can be put in an assembly. The results presented in this paper are a component of the automated design of parts orienting devices. The focus is on orienting parts with minimal sensing and manipulation. We present a new approach to parts orienting through the manipulation of pose distributions. Through dynamic simulation we can determine the pose distribution for an object being dropped from an arbitrary height on an arbitrary surface. By varying the drop height and the shape of the support surface we can find the initial conditions that will result in a pose distribution with minimal entropy. We are trying to uniquely orient a part with high probability just by varying the initial conditions. We will derive a condition on the pose and velocity of a simple planar object in contact with a sloped surface that will allow us to quickly determine the final resting configuration of the object. This condition can then be used to quickly compute the pose distribution. We also present simulation and experimental results that show how dynamic simulation can be used to find optimal shapes and drop heights for a given part.
On Delaying Collision Checking in PRM Planning: Application to Multi-Robot Coordination
Authors: Sánchez Gildardo , Latombe Jean-Claude
Published: July 2003

This paper describes the foundations and algorithms of a new probabilistic roadmap (PRM) planner that is: single-query —instead of pre-computing a roadmap covering the entire free space, it uses the two input query configurations to explore as little space as possible; bi-directional —it explores the robot's free space by building a roadmap made of two trees rooted at the query configurations; and lazy in checking collisions —it delays collision tests along the edges of the roadmap until they are absolutely needed. Several observations motivated this strategy: (1) PRM planners spend a large fraction of their time testing connections for collision; (2) most connections in a roadmap are not on the final path; (3) the collision test for a connection is most expensive when there is no collision; and (4) any short connection between two collision-free configurations has high prior probability of being collision-free. The strengths of single-query and bi-directional sampling techniques and those of delayed collision checking reinforce each other. Experimental results show that this combination reduces planning time by a large factor, making it possible to efficiently handle difficult planning problems, such as problems involving multiple robots in geometrically complex environments. This paper specifically describes the application of the planner to multi-robot planning and compares results obtained when the planner uses a centralized planning approach (PRM planning is then performed in the joint configuration space of the robots) and when it uses a decoupled approach (the PRM planner is invoked several times, first to compute a path of each robot independent of the others, and then to coordinate those paths). On a simulated six-robot welding station combining 36 degrees of freedom, centralized planning has proven to be a much more effective approach than decoupled planning.
Motion Guides for Assisted Manipulation
Authors: Lynch Kevin M. , Caizhen Liu  , Sørensen Allan , Kim Songho , Peshkin Michael , Colgate J. Edward , Tickel Tanya , Hannon David , Shiels Kerry
Published: July 2003

This paper explores the use of passive guides to assist a human in manipulating heavy loads. A guide acts as a frictionless rail which confines the load to a one-dimensional curve in its configuration space. In this paper we formulate the problem of designing guides to effectively assist the human, and we apply the formulation to two types of materials handling tasks: pushing a heavy cart and single-arm reaching motions. Guides may be implemented by fixed rails or programmable constraint machines. Initial experiments with humans suggest the potential benefits of guided manipulation.
An Autonomous Crop Treatment Robot: Part I. A Kalman Filter Model for Localization and Crop/Weed Classification
Authors: Southall B. , Hague T. , Marchant J.A. , Buxton B.F.
Published: July 2003

This work is concerned with a machine vision system for an autonomous vehicle designed to treat horticultural crops. The vehicle navigates by following rows of crop (individual cauliflower plants) that are planted in a reasonably regular array typical of commercial practice. We adopt an extended Kalman filter approach where the observation model consists of a grid which is matched to the crop planting pattern in the perspective view through the vehicle camera. Plant features are extracted by thresholding near infrared images of the scene evolving before the camera. A clustering method collects the features into groups representing single plants. An important aspect of the approach is that it provides both localization information and crop/weed discrimination within a single framework, since we can assume that features not matching the planting pattern are weeds.

Off-line tests with two image sequences are carried out to compare the tracking with assessment by three different humans. These show that the extended Kalman filter is a viable method for tracking and that the model parameters derived from the filter are consistent with human assessment.

We conclude that the performance will be good enough for accurate in-field navigation.
An Autonomous Crop Treatment Robot: Part II. Real Time Implementation
Authors: Hague T. , Southall B. , Tillett N.D.
Published: July 2003

Implementation of an autonomous vehicle for precision treatment of crop plants is described. The navigation system integrates the vision system described in Part I with inertial and odometric sensing. A modular approach is adopted, where the crop grid observation model is re-formulated as a non-linear compression filter, which combines a set of observations of crop plants into a single pseudo-observation of the position of the crop planting grid relative to the vehicle position. The compression filter encapsulates all internal detail of the vision system (camera calibration, crop layout, etc.). The output from this vision module can be used as an observation in the conventional way by the vehicle's navigation Kalman filter.

Plant features classified into crop and weed by the vision module are registered into a treatment map. The need to treat targets from a moving platform requires time delays in the processing of observations to be considered. A method of compensation is introduced which allows time delayed vision observations to be used; the effectiveness of the technique is illustrated by an example with an artificially extended time delay.

In field trials of the vehicle have been performed, and the accuracy of both vehicle navigation and crop treatment are reported. We conclude that the navigation accuracy falls within the 20 mm root mean square error region thought appropriate for precise horticultural operations, and that spray application is sufficiently accurate for the treatment of individual crop plants.
Persistent Passive Hopping and Juggling is Possible Even With Plastic Collisions
Authors: Chatterjee A. , Pratap R. , Reddy C.K. , Ruina A.
Published: July 2003

We describe simple one-dimensional models of passive (no energy input, no control), generally dissipative, vertical hopping and one-ball juggling. The central observation is that internal passive system motions can conspire to eliminate collisions in these systems. For hopping, two point masses are connected by a spring and the lower mass has inelastic collisions with the ground. For juggling, a lower point-mass hand is connected by a spring to the ground and an upper point-mass ball is caught with an inelastic collision and then re-thrown into gravitational free flight. The two systems have identical dynamics. Despite inelastic collisions between non-zero masses, these systems have special symmetric energy-conserving periodic motions where the collision is at zero relative velocity. Additionally, these special periodic motions have a non-zero sized, one-sided region of attraction on the higher-energy side. For either very large or very small mass ratios, the one-sided region of attraction is large. These results persist for mildly non-linear springs and non-constant gravity. Although non-collisional damping destroys the periodic motions, small energy injection makes the periodic motions stable, with a two-sided region of attraction. The existence of such special energy conserving solutions for hopping and juggling points to possibly useful strategies for both animals and robots. The lossless motions are demonstrated with a table-top experiment.
Controlling an Uninstrumented Manipulator By Visual Servoing
Authors: Marchand Eric , Chaumette François , Spindler Fabien , Perrier Michel
Published: July 2003

In this paper we present a method to control the displacement of a robot arm with no proprioceptive sensor. The joint positions are not available and this manipulator is usually open-loop controlled. In order to get a more efficient control interface, we propose a closed-loop system based on an eye-to-hand visual servoing approach. We show that, using such an approach, measurement of the manipulator motion with proprioceptive sensors is not required to precisely control the end-effector motion. We propose solutions for position-based control and velocity control of the manipulator. To maintain the end effector in the camera field of view, the camera orientation is also controlled. Various results show the validity and the efficiency of the approach.
Design of a Parallel-Type Gripper Mechanism
Authors: Yi Byung-Ju , Heung Yeol Na  , Jae Hoon Lee  , Hong Yeh-Sun , Oh Sang-Rok , Il Hong Suh  , Whee Kuk Kim
Published: July 2003

A new parallel-type gripper mechanism is proposed in this work. This device has a parallelogramic platform that can be flexibly folded. Therefore, this mechanism not only can be used to grasp an object having irregular shape or large volume, but also can be utilized as a micro-positioning device after grasping objects. Forward position analysis and platform kinematics are investigated to deal with motion tracking and force control. Kinematic optimization is performed to design a parallel-type gripping mechanism so that it can reach the specified workspace, span the given range of the specified configuration parameters, and generate a desired force to grasp an object. A pneumatic rotator is employed for actuation and a miniaturized proportional 4/3 -way directional valve is specially developed to deal with feedback-based dynamic control. The proportional valve allows indirect force control by measuring the offset-load pressure raised by the contact between the grasped object and the parallel platform. In experimental work, the performance of the motion tracking and indirect force control has been shown to be successful.
Computing Camera Viewpoints in an Active Robot Work Cell
Authors: Abrams Steven , Allen Peter K. , Tarabanis Konstantinos
Published: July 2003

This paper presents a dynamic sensor-planning system that is capable of planning the locations and settings of vision sensors for use in an environment containing objects moving in known ways. The key component of this research is the computation of the camera position, orientation, and optical settings to be used over a time interval. A new algorithm is presented for viewpoint computation which ensures that the feature-detectability constraints of focus, resolution, field of view, and visibility are satisfied. A five-degree-of-freedom Cartesian robot carrying a CCD camera in a hand/eye configuration and surrounding the work cell of a Puma 560 robot was constructed for performing sensor-planning experiments. The results of these experiments, demonstrating the use of this system in a robot work cell, are presented.
Hand-Eye Calibration Using Dual Quaternions
Authors: Daniilidis Konstantinos
Published: July 2003

To relate measurements made by a sensor mounted on a mechanical link to the robot’s coordinate frame, we must first estimate the transformation between these two frames. Many algorithms have been proposed for this so-called hand-eye calibration, but they do not treat the relative position and orientation in a unified way. In this paper, we introduce the use of dual quaternions, which are the algebraic counterpart of screws. Then we show how a line transformation can be written with the dual-quaternion product. We algebraically prove that if we consider the camera and motor transformations as screws, then only the line coefficients of the screw axes are relevant regarding the hand-eye calibration. The dual-quaternion parameterization facilitates a new simultaneous solution for the hand-eye rotation and translation using the singular value decomposition. Real-world performance is assessed directly in the application of hand-eye information for stereo reconstruction, as well as in the positioning of cameras. Both real and synthetic experiments show the superiority of the approach over two other proposed methods.
Caging Planar Bodies by One-Parameter Two-Fingered Gripping Systems
Authors: Rimon Elon , Blake Andrew
Published: July 2003

This paper is concerned with a caging problem: we wish to surround an object B by a multifingered hand such that B has some freedom to move, but still cannot escape the “cage” formed by the fingers. We introduce a new notion of the caging set, which is based on the configuration-space representation of the free motions of the hand system with respect to the object. Using stratified Morse theory, we show that the hand’s configuration at which the cage is broken corresponds to a frictionless equilibrium grasp. This allows us to formulate a technique for computing the caging set of a two-fingered hand whose opening is controlled by a single parameter. The tech-nique generalizes to one-parameter grip ping systems having a higher number of fingers.
Position Control of Robot Manipulators Manipulating a Flexible Payload
Authors: Sun Dong , Mills James K. , Liu Yunhui
Published: July 2003

Robotic manipulation of a flexible payload is a complex and challenging control problem. This paper demonstrates from both theoretical and experimental perspectives that through proper design of the control gains, the simple scheme of PD plus gravity compensation can control a flexible payload manipulated by multiple robots to a desired position/orientation while damping the vibrations of the payload at each contact. The suppression of the vibration at each contact is helpful to suppress all vibrations of the flexible body. If the payload has a large stiffness or small mass, the proposed scheme can regulate the deformations at the contacts to zero, and also, the offsets of all static deformations of the payload with reference to the original positions decay to zero. A “clamped-free” model is used to decompose the dynamics of the payload into two distinct dynamic subsystems. This allows us to treat these dynamic subsystems separately and prove that desired motion trajectories can be achieved with the proposed scheme. As an example, the experiment of manipulating a flexible sheet using two CRS A460 robots is further described.
Massively Parallel Nanorobotics for Lithography and Data Storage
Authors: Requicha Aristides A. G.
Published: July 2003

Nanometer-scale structures and devices can be constructed by using the tip of a scanning probe microscope (SPM) as a robot. The tip manipulates nanocomponents to build assemblies, or induces material deposition to form patterns on a substrate. Fabrication by SPM methods has severe throughput problems, which can be solved by using arrays of tips built by MEMS (MicroElectroMechanical Systems) technology, in conjunction with the strategies and algorithms presented in this paper. Massively parallel methods are described here for writing and reading nanometer-scale patterns of lines or dots, or for manipulating nanoparticles with arrays of SPM tips. The tip array moves as a whole in the x, y plane of the substrate, and does not require individual x, y drives and controllers for the individual tips. Applications to nanolithography are discussed, as well as a microelectromechanical storage device, analogous to a compact disc (CD) on a chip, and called an editable nanoCD. NanoCDs can be read and edited by the tip-array methods presented here, and have bit densities and reading speeds that are several orders of magnitude higher than those of current CDs.
In-Hand Dexterous Manipulation of Piecewise-Smooth 3-D Objects
Authors: Rus Daniela
Published: July 2003

We present an algorithm called finger tracking for in-hand manipulation of three-dimensional objects with independent robot fingers. We describe and analyze the differential control for finger tracking and extend it to on-line continuous control for a set of cooperating robot fingers. We show experimental data from a simulation. Finally, we discuss global control issues for finger tracking, and compute lower bounds for reorientation by finger tracking. Our algorithm is computationally efficient, exact, and takes into consideration the full dynamics of the system.
Voting as Validation in Robot Programming
Authors: Utete Simukai W. , Barshan Billur , Ayrulu Birsel
Published: July 2003

This paper investigates the use of voting as a conflict-resolution technique for data analysis in robot programming. Voting represents an information-abstraction technique. It is argued that in some cases a voting approach is inherent in the nature of the data being analyzed: where multiple, independent sources of information must be reconciled to give a group decision that reflects a single outcome rather than a consensus average. This study considers an example of target classification using sonar sensors. Physical models of reflections from target primitives that are typical of the indoor environment of a mobile robot are used. Dispersed sensors take decisions on target type, which must then be fused to give the single group classification of the presence or absence and type of a target. Dempster-Shafer evidential reasoning is used to assign a level of belief to each sensor decision. The decisions are then fused by two means. Using Dempster’s rule of combination, conflicts are resolved through a group measure expressing dissonance in the sensor views. This evidential approach is contrasted with the resolution of sensor conflict through voting. It is demonstrated that abstraction of the level of belief through voting proves useful in resolving the straightforward conflicts that arise in the classification problem. Conflicts arise where the discriminant data value, an echo amplitude, is most sensitive to noise. Fusion helps to overcome this vulnerability: in Dempster-Shafer reasoning, through the modeling of nonparametric uncertainty and combination of belief values; and in voting, by emphasizing the majority view. The paper gives theoretical and experimental evidence for the use of voting for data abstraction and conflict resolution in areas such as classification, where a strong argument can be made for techniques that emphasize a single outcome rather than an estimated value. Methods for making the vote more strategic are also investigated. The paper addresses the reduction of dimension of sets of decision points or decision makers. Through a consideration of combination order, queuing criteria for more strategic fusion are identified.
Robust Cooperative Control of Two Two-Link Flexible Manipulators on the Basis of Quasi-Static Equations
Authors: Matsuno Fumitoshi , Hatayama Michinori
Published: July 2003

In this paper, a dynamic model of a distributed parameter system and a control architecture are developed for the closed-chain motion of two two-link flexible manipulators holding a common rigid object in a horizontal workspace. We derive the dynamic relation of deformation of the flexible links, constraint force, and rigid-object dynamics. Use of the quasi-static relation of the deformation, the constraint force, and the rigid-object dynamics gives quasi-static equations of joint angles which are not dependent on the variables related to the deformations of the flexible links. We design a robust cooperative controller of the two flexible manipulators considering measurement disturbances and modeling errors caused by the link-parameter uncertainty and the quasi-static approximation. A set of experiments for the cooperative control of the two flexible manipulators using a force sensor has been carried out. Several experimental results are shown.
Postural Stability of Biped Robots and the Foot-Rotation Indicator (FRI) Point
Authors: Goswami Ambarish
Published: July 2003

The focus of this paper is the problem of foot rotation in biped robots during the single-support phase. Foot rotation is an indication of postural instability, which should be carefully treated in a dynamically stable walk and avoided altogether in a statically stable walk.

We introduce the foot-rotation indicator (FRI) point, which is a point on the foot/ground-contact surface where the net ground-reaction force would have to act to keep the foot stationary. To ensure no foot rotation, the FRI point must remain within the convex hull of the foot-support area.

In contrast with the ground projection of the center of mass (GCoM), which is a static criterion, the FRI point incorporates robot dynamics. As opposed to the center of pressure (CoP)—better known as the zero-moment point (ZMP) in the robotics literature—which may not leave the support area, the FRI point may leave the area. In fact, the position of the FRI point outside the footprint indicates the direction of the impending rotation and the magnitude of rotational moment acting on the foot. Owing to these important properties, the FRI point helps not only to monitor the state of postural stability of a biped robot during the entire gait cycle, but indicates the severity of instability of the gait as well. In response to a recent need, the paper also resolves the misconceptions surrounding the CoP/ZMP equivalence.
Sequential Composition of Dynamically Dexterous Robot Behaviors
Authors: Burridge R. R. , Rizzi A. A. , Koditschek D. E.
Published: July 2003

We report on our efforts to develop a sequential robot controller-composition technique in the context of dexterous “batting” maneuvers. A robot with a flat paddle is required to strike repeatedly at a thrown ball until the ball is brought to rest on the paddle at a specified location. The robot’s reachable workspace is blocked by an obstacle that disconnects the free space formed when the ball and paddle remain in contact, forcing the machine to “let go” for a time to bring the ball to the desired state. The controller compositions we create guarantee that a ball introduced in the “safe workspace” remains there and is ultimately brought to the goal. We report on experimental results from an implementation of these formal composition methods, and present descriptive statistics characterizing the experiments.
An Explanation of Never-Special Assembly Changing Motions for 3–3 Parallel Manipulators
Authors: McAree P. R. , Daniel R. W.
Published: July 2003

When the leg rods of a fully in-parallel manipulator are fixed in their lengths, it is usual that the device can be assembled in several distinct ways. Sometimes it happens that motion between such assemblies can take place such that the linkage is never at a special configuration; that is, a configuration where the moving-platform body acquires uncontrollable freedom relative to the base. The possibility of such motion has implications for control. Focusing on 3–3 devices, we present a geometric explanation of how these motions arise, and give a sufficient condition for their existence. For the 3–3 planar-motion device, we show that never-special assembly changing motions can be excluded by making platform and base triangles similar, and we conjecture that appropriate, perhaps identical, specialization for the octahedral manipulator has the same effect.
Shape Control of Manipulators with Hyper Degrees of Freedom
Authors: Mochiyama Hiromi , Shimemura Etsujiro , Kobayashi Hisato
Published: July 2003

This paper provides a theoretical framework for controlling a manipulator with hyper degrees of freedom (HDOF). An HDOF manipulator has the capability to achieve various kinds of tasks. To make full use of its capability, shape control is proposed here; that is, not only the tip of a manipulator, but also its whole body is controlled. To formulate control objectives for shape control, we define a shape correspondence between an HDOF manipulator and a spatial curve that prescribes a desired shape. The shape correspondence is defined by using solutions of a nonlinear optimization problem termed the shape-inverse problem. We give theorems on the existence of the solutions, and on an existence region that allows us to convert shape-control problems into more tractable ones. A shape-regulation control problem is considered first to bring an HDOF manipulator onto a given time-invariant curve. The idea of estimating the desired curve parameters is the crucial key to solving the problem by Lyapunov design. The derived shape-regulation law includes the estimator, which infers the desired curve parameters corresponding to the desired joint positions on the curve. The idea of the desired curve-parameter estimation is also effective for shape tracking where a time-varying curve is used for prescribing a moving desired shape. Considering an estimator with second-order dynamics enables us to find two shape-tracking control laws by utilizing conventional tracking methods in manipulator control. We show the simulation results of applying the derived shape-tracking control laws to a 20-DOF manipulator.
Computation of Robot Configuration and Workspaces via the Fourier Transform on the Discrete-Motion Group
Authors: Kyatkin Alexander B. , Chirikjian Gregory S.
Published: July 2003

We apply the Fourier transform on the discrete-motion group to the problem of computing the configuration-space obstacles of mobile robots which move among static obstacles, the problem of finding the workspace density of binary manipulators with many actuators, and the problem of determining workspace boundaries of manipulators with continuous-motion actuators. We develop and implement Fourier transforms for the discrete-motion group of the plane. These transforms allow us to apply fast Fourier transform methods to the computation of convolution-like integrals that arise in robot kinematics and motion planning. The results of the implementation are discussed for particular examples.
Dante II: Technical Description, Results, and Lessons Learned
Authors: Bares John E. , Wettergreen David S.
Published: July 2003

Dante II is a unique walking robot that provides important insight into high-mobility robotic locomotion and remote robotic exploration. Dante II’s uniqueness stems from its combined legged and rappelling mobility system, its scanning-laser rangefinder, and its multilevel control scheme. In 1994 Dante II was deployed and successfully tested in a remote Alaskan volcano, as a demonstration of the fieldworthiness of these technologies. For more than five days the robot explored alone in the volcano crater using a combination of supervised autonomous control and teleoperated control. Human operators were located 120 km distant during the mission. This article first describes in detail the robot, support systems, control techniques, and user interfaces. We then describe results from the battery of field tests leading up to and including the volcanic mission. Finally, we put forth important lessons which comprise the legacy of this project. We show that framewalkers are appropriate for rappelling in severe terrain, though tether systems have limitations. We also discuss the importance of future “autonomous” systems to realize when they require human support rather than relying on humans for constant oversight.
Adaptive Mobile Robot Navigation and Mapping
Authors: Feder Hans Jacob S. , Leonard John J. , Smith Christopher M.
Published: July 2003

The task of building a map of an unknown environment and concurrently using that map to navigate is a central problem in mobile robotics research. This paper addresses the problem of how to perform concurrent mapping and localization (CML) adaptively using sonar. Stochastic mapping is a feature-based approach to CML that generalizes the extended Kalman filter to incorporate vehicle localization and environmental mapping. The authors describe an implementation of stochastic mapping that uses a delayed nearest neighbor data association strategy to initialize new features into the map, match measurements to map features, and delete out-of-date features. The authors introduce a metric for adaptive sensing that is defined in terms of Fisher information and represents the sum of the areas of the error ellipses of the vehicle and feature estimates in the map. Predicted sensor readings and expected dead-reckoning errors are used to estimate the metric for each potential action of the robot, and the action that yields the lowest cost (i.e., the maximum information) is selected. This technique is demonstrated via simulations, in-air sonar experiments, and underwater sonar experiments. Results are shown for (1) adaptive control of motion and (2) adaptive control of motion and scanning. The vehicle tends to explore selectively different objects in the environment. The performance of this adaptive algorithm is shown to be superior to straight-line motion and random motion.
Navigation Results from Desert Field Tests of the Rocky 7 Mars Rover Prototype
Authors: Volpe Richard
Published: July 2003

Upcoming missions to the surface of Mars will use mobile robots to traverse long distances from the landing site. To prepare for these missions, the prototype rover, Rocky 7, has been tested in desert field trials conducted with a team of planetary scientists. While several new capabilities have been demonstrated, foremost among these was sun-sensor-based traversal of natural terrain totaling a distance of 1 km. This paper describes navigation results obtained in the field tests, where cross-track error was only 6% of the distance traveled. Comparison with previous results of other planetary rover systems shows this to be a significant improvement. Methods for further improvement are also discussed.
Robots in Human Environments: Basic Autonomous Capabilities
Authors: Khatib O. , Yokoi K. , Brock O. , Chang K. , Casal A.
Published: July 2003

This article discusses the basic capabilities needed to enable robots to operate in human-populated environments for accomplishing both autonomous tasks and human-guided tasks. These capabilities are key to many new emerging robotic applications in service, construction, field, underwater, and space. An important characteristic of these robots is the “assistance” ability they can bring to humans in performing various physical tasks. To interact with humans and operate in their environments, these robots must be provided with the functionality of mobility and manipulation. The article presents developments of models, strategies, and algorithms concerned with a number of autonomous capabilities that are essential for robot operations in human environments. These capabilities include: integrated mobility and manipulation, cooperative skills between multiple robots, interaction ability with humans, and efficient techniques for real-time modification of collision-free path. These capabilities are demonstrated on two holonomic mobile platforms designed and built at Stanford University in collaboration with Oak Ridge National Laboratories and Nomadic Technologies.
A Sensor System for the Navigation of an Underwater Vehicle
Authors: Smith Robert , Frost Andy , Probert Penny
Published: July 2003

A sensor system for an underwater vehicle is described. The vehicle is equipped with inclinometers, gyroscopes, a magnetometer, a pressure gauge, and a sonar system. The sensor models used for the inclinometers and gyroscopes are straightforward; however, the magnetometer can be corrupted by variations in the earth’s field caused by: external objects and internal magnetic fields. We show how to use inclinometer data to adjust for a limited set of external field variation. We also show how to calibrate the magnetometer to compensate for static and thruster-dependent internal fields. The sonar unit uses range differentials between cheap time-of-flight sonar to follow a target. This reduces signal processing since data association is only required on target acquisition, and removes the need to scan an entire landscape, which is usually slow. The gyroscopes are fused via a second indirect filter system. The vehicle attitude is represented as a quaternion; these have a low computational burden, and lack discontinuities and singularities. The simplicity of the indirect filter permits very fast update rates, so that the system may follow rapid vehicle rotations.
Navigating a Robotic Wheelchair in a Railway Station during Rush Hour
Authors: Prassler E. , Scholz J. , Fiorini P.
Published: July 2003

This paper describes the hardware design, control, and navigation system of and some preliminary experiments with the robotic wheelchair Mobility Aid for elderly and disabled people (MAid). MAid’s general task is to transport people with severely impaired motion skills. The authors did not set out to reinvent and redevelop the set of standard skills of so-called intelligent wheelchairs, such as Follow Wall, FollowCorridor, PassDoorway, which are commonly described in the literature. These maneuvers require motion control skills that disabled people, in spite of their disabilities, are eager to learn and quite good at using. Instead, this work focused on generalizing the approach to fine motion control by considering those maneuvers identified as very burdensome due to their duration and required concentration. One of these functions is deliberative locomotion in rapidly changing, large-scale environments, such as shopping malls, entry halls of theaters, and concourses of airports or railway stations, where tens or hundreds of people and objects move around. MAid’s performance was tested in the central station of Ulm during rush hour and in the exhibition halls of the Hannover Messe ’98, the largest industrial fair in the world. Altogether, MAid has survived more than 36 h of testing in public, crowded environments with heavy passenger traffic.
Dynamic Mobility with Single-Wheel Configuration
Authors: Xu Yangsheng , Brown H. Ben , Au Kwok Wai
Published: July 2003

This paper presents a novel concept of mobility that provides dynamic stability and rapid locomotion. The concept, called Gyrover, is a single-wheel, gyroscopically stabilized robot that can be considered as a single wheel actuated by a spinning flywheel attached to a two-link manipulator at the wheel bearing and drive motor. The spinning flywheel acts as a gyroscope to stabilize the robot, and it can be tilted to achieve steering. This configuration conveys significant advantages over multiwheel, statically stable vehicles, including good dynamic stability and insensitivity to attitude disturbances, high maneuverability, low rolling resistance, ability to recover from falls, and amphibious capability. In this paper, the authors present the robot concept, three prototypes of the design, and system implementation. The authors study the robot’s nonholonomic constraints and the stabilizing effect of the flywheel on the system through simulation and experiments.
Development of a 3500-Tonne Field Robot
Authors: Roberts Jonathan M. , Corke Peter I. , Winstanley Graeme J.
Published: July 2003

The mining industry is highly suitable for the application of robotics and automation technology, since the work is arduous, dangerous, and often repetitive. This paper presents a broad overview of the issues involved in the development of a physically large and complex field robotic system—a 3500-tonne mining machine (dragline). Draglines are “walking cranes” used in open-pit coal mining to remove the material covering a coal seam. The critical issues of robust load position sensing, modeling of the dynamics of the electrical drive system and the swinging load, control strategies, the operator interface, and automation system architecture are addressed. An important aspect of this system is that it must work cooperatively with a human operator, seamlessly passing control back and forth in order to achieve the main aim—increased productivity.
Shape Description of Curved Surfaces from Contact Sensing Using Surface Normals
Authors: Charlebois M. , Gupta K. , Payandeh S.
Published: July 2003

We describe a spline-based framework for incorporating both position and surface-normal information into estimates of curvaturebased shape parameters. Such position and normal data can be obtained with different types of contact sensors, for example, tactile sensors, force-moment sensors, etc. The heart of our framework is an extended B-spline formulation that incorporates the surfacenormal information into a B-spline surface fit of the position data. The surface-normal information provides additional constraints for the surface fit, and can also significantly improve the approximation of the surface. Curvature-based shape parameters applied to this B-spline surface are then used to characterize the local shape of the object surface. Preliminary experiments with simple primitives—spherical, cylindrical, and planar shapes—and an off theshelf force/moment sensor to obtain the position and surfacenormal data show that despite coarse resolution of the sensor, this approach succeeds in qualitative shape recognition.
Surface Profile Determination from Multiple Sonar Data Using Morphological Processing
Authors: Baskent Deniz , Barshan Billur
Published: July 2003

This paper presents a novel method for surface profile determination using multiple sensors. Our approach is based on morphological processing techniques to fuse the range data from multiple sensor returns in a manner that directly reveals the target surface profile. The method has the intrinsic ability of suppressing spurious readings due to noise, crosstalk, and higher-order reflections, as well as processing multiple reflections informatively. The approach taken is extremely flexible and robust, in addition to being simple and straightforward. It can deal with arbitrary numbers and configurations of sensors as well as synthetic arrays. The algorithm is verified both by simulations and experiments in the laboratory by processing real sonar data obtained from a mobile robot. The results are compared to those obtained from a more accurate structured-light system, which is, however, more complex and expensive.
Efficient Camera-Space Target Disposition in a Matrix of Moments Structure Using Camera-Space Manipulation
Authors: González-Galván Emilio J. , Seelinger Michael J.
Published: July 2003

This paper introduces a newestimation approach for determining the sequence of internal manipulator configurations which are required to perform a task on an arbitrarily positioned and oriented workpiece, in the context of the method of camera-space manipulation— a robust and precise means of controlling three-dimensional robot maneuvers using vision. Despite a nonlinear estimation model, a recursive scheme is developed. This approach reduces the computational and memory burden that is required by the “batch” estimation approach while retaining identical results. The same formalism that permits this result is used to condense to a minimum the visual information required to create “camera-space objectives.” The discussion includes actual experimental results wherein robust, millimeter six-axis positioning precision with a three-dimensional, rigid-body task is achieved using a very large GMF S-400 robot.
Static Balancing of Spherical 3-DOF Parallel Mechanisms and Manipulators
Authors: Gosselin Clément M.
Published: July 2003

The static balancing of spherical three-degree-of-freedom (DoF) parallel mechanisms and manipulators is addressed in this paper. Static balancing is defined here as the set of conditions on mechanism dimensional and inertial parameters which, when satisfied, ensure that the weight of the links does not produce any torque (or force) at the actuators for any configuration of the mechanism, under static conditions. First, the static balancing of a single body mounted on a spherical joint is studied. It is shown that it is possible to balance such a mechanism with springs, and that complete balancing can be achieved even with a single spring. Geometric conditions for the location of the spring attachments are given. Then, the results are applied to the balancing of two types of 3-DoF spherical parallel mechanisms. The first mechanism is a 9R manipulator, while the second one is referred to as the 3-6-6 spherical mechanism. For each of these mechanisms, the balancing conditions are first derived for systems in which no springs are used. Then, conditions for the balancing using springs are obtained. Static balancing leads to considerable reduction in the actuator torques (or forces), which in turn allows the use of less powerful actuators and therefore leads to more efficient designs. Hence, the balancing conditions derived here are of great interest in a context of design.