waashk/dblp huggingface dataset:
corn plant sensing using real-time stereo vision. though some two-dimensional (2d) machine vision&ndash;based systems for early-growth-stage corn plant sensing exist, some of their shortcomings are difficult to overcome. the greatest challenge comes from separating individual corn plants with overlapped plant canopies. with 2d machine vision, variation in outdoor lighting conditions and weeds in the background also pose difficulties in corn plant identification. adding the depth dimension has the potential to improve the performance of such a sensing system. a new corn plant sensing system using a real-time stereo vision system was investigated in this research. top-view depth images of corn plant canopy were acquired. by processing the depth images, the algorithm effectively updated the plant skeleton structures and finally recognized individual corn plants and detected their center positions. the stereo vision system was tested over corn plants of v2&ndash;v3 growth stages in both laboratory and field conditions. experimental results showed that the stereo vision system was capable of detecting both separated and overlapped corn plants. during the field test, 96.7&percnt; of the corn plants were correctly detected, and plant center positions were estimated with maximum distance errors of 5 and 1 cm for 74.6&percnt; and 62.3&percnt; of detections, respectively. &copy; 2009 wiley periodicals, inc.
toward extraplanetary under-ice exploration: robotic steps in the arctic. this paper describes the design and use of two new autonomous underwater vehicles, jaguar and puma, which were deployed in the summer of 2007 at sites at 85&deg;n latitude in the ice-covered arctic ocean to search for hydrothermal vents. these robots are the first to be deployed and recovered through ice to the deep ocean (>3,500 m) for scientific research. we examine the mechanical design, software architecture, navigation considerations, sensor suite, and issues with deployment and recovery in the ice based on the missions they carried out. successful recoveries of vehicles deployed under the ice require two-way acoustic communication, flexible navigation strategies, redundant localization hardware, and software that can cope with several different kinds of failure. the ability to direct an autonomous underwater vehicle via the low-bandwidth and intermittently functional acoustic channel is of particular importance. on the basis of our experiences, we also discuss the applicability of the technology and operational approaches of this expedition to the exploration of jupiter's ice-covered moon europa. &copy; 2009 wiley periodicals, inc.
learning terrain segmentation with classifier ensembles for autonomous robot navigation in unstructured environments. autonomous robot navigation in unstructured outdoor environments is a challenging area of active research and is currently unsolved. the navigation task requires identifying safe, traversable paths that allow the robot to progress toward a goal while avoiding obstacles. stereo is an effective tool in the near field, but used alone leads to a common failure mode in autonomous navigation in which suboptimal trajectories are followed due to nearsightedness, or the robot's inability to distinguish obstacles and safe terrain in the far field. this can be addressed through the use of machine learning methods to accomplish near-to-far learning, in which near-field terrain appearance and stereo readings are used to train models able to predict far-field terrain. this paper proposes to enhance existing, memoryless near-to-far learning approaches through the use of classifier ensembles that allow terrain models trained on data seen at different points in time to be preserved and referenced later. these stored models serve as memory, and we show that they can be leveraged for more effective far-field terrain classification on future images seen by the robot. a five-factor, full-factorial, repeated-measures experimental evaluation is performed on hand-labeled data sets taken directly from the problem domain. the experiments result in many statistically significant findings, the most important being that the proposed near-to-far best-k ensemble algorithm, with appropriate parameter selection, outperforms the single-model, nonensemble baseline approach in far-field terrain classification. several other findings that inform the use of near-to-far ensemble methods are also presented. &copy; 2009 wiley periodicals, inc.
slope traversal controls for planetary exploration rover on sandy terrain. in this paper, two control approaches are presented for exploration rovers traversing sandy-sloped terrain. one of the proposed controls is a model-based feed-forward control using a characteristic diagram, called a thrust-cornering characteristic diagram. it consists of various characteristic curves of wheel forces for varied wheel slip conditions. an appropriate steering maneuver for slope traversal can be found using the diagram with slope traversal criteria. the other control is a sensor-based feedback control. a key approach to this feedback control is to compensate for three types of slip, namely, the vehicle sideslip and longitudinal-lateral slips of a wheel. the feedback control calculates both steering and driving maneuvers that can compensate for these slips and also allow the rover to successfully traverse a sandy slope. the performances of these two control approaches are confirmed in slope traversal experiments using a four-wheeled rover test bed. the proposed controls are verified by quantitative evaluations of distance and orientation errors. through the experiment, it was found that the two controls have advantages and disadvantages, and the possibility of merging the model-based control and the sensor-based control is discussed. &copy; 2009 wiley periodicals, inc.
automatic guidance of a four-wheel-steering mobile robot for accurate field operations. as world population growth requires an increasing level of farm production at the same time that environmental preservation is a priority, the development of new agricultural tools and methods is required. in this framework, the development of robotic devices can provide an attractive solution, particularly in the field of autonomous vehicles. accurate automatic guidance of mobile robots in farming constitutes a challenging problem for researchers, mainly due to the low grip conditions usually found in such a context. from assisted-steering systems to agricultural robotics, numerous control algorithms have been studied to achieve high-precision path tracking and have reached an accuracy within &plusmn;10 cm, whatever the ground configuration and the path to be followed. however, most existing approaches consider classical two-wheel-steering vehicles. unfortunately, by using such a steering system, only the lateral deviation with respect to the path to be followed can be satisfactorily controlled. indeed, the heading of the vehicle remains dependent on the grip conditions, and crabwise motions, for example, are systematically observed on a slippery slope, leading to inaccurate field operations. to tackle this drawback, a four-wheel-steering (4ws) mobile robot is considered, enabling servo of both lateral and angular deviations with respect to a desired trajectory. the path tracking control is designed using an extended kinematic representation, allowing account to be taken online of wheel skidding, while a backstepping approach permits management of the 4ws structure. the result is an approach taking advantage of both rear and front steering actuations to fully compensate for sliding effects during path tracking. moreover, a predictive algorithm is developed in order to address delays induced by steering actuators, compensating for transient overshoots in curves. experimental results demonstrate that despite sliding phenomena, the mobile robot is able to automatically and accurately achieve a desired path, with lateral and angular errors, respectively, within &plusmn;10 cm and &plusmn;2 deg, whatever its shape and whatever the terrain conditions. this constitutes a promising result in efforts to define efficient tools with which to tackle tomorrow's agriculture challenge. &copy; 2009 wiley periodicals, inc.
gamma-slam: visual slam in unstructured environments using variance grid maps. this paper describes an online stereo visual simultaneous localization and mapping (slam) algorithm developed for the learning applied to ground robotics (lagr) program. the gamma-slam algorithm uses a rao&ndash;blackwellized particle filter to obtain a joint posterior over poses and maps: the pose distribution is estimated using a particle filter, and each particle has its own map that is obtained through exact filtering conditioned on the particle's pose. visual odometry is used to provide good proposal distributions for the particle filter, and maps are represented using a cartesian grid. unlike previous grid-based slam algorithms, however, the gamma-slam map maintains a posterior distribution over the elevation variance in each cell. this variance grid map can capture rocks, vegetation, and other objects that are typically found in unstructured environments but are not well modeled by traditional occupancy or elevation grid maps. the algorithm runs in real time on conventional processors and has been evaluated for both qualitative and quantitative accuracy in three outdoor environments over trajectories totaling 1,600 m in length. &copy; 2008 wiley periodicals, inc.
targeted driving using visual tracking on mars: from research to flight. this paper presents the development, validation, and deployment of the visual target tracking capability onto the mars exploration rover (mer) mission. visual target tracking enables targeted driving, in which the rover approaches a designated target in a closed visual feedback loop, increasing the target position accuracy by an order of magnitude and resulting in fewer ground-in-the-loop cycles. as a result of an extensive validation, we developed a reliable normalized cross-correlation visual tracker. to enable tracking with the limited computational resources of a planetary rover, the tracker uses the vehicle motion estimation to scale and roll the template image, compensating for large image changes between rover steps. the validation showed that a designated target can be reliably tracked within several pixels or a few centimeters of accuracy over a 10-m traverse using a rover step size of 10% of the target distance in any direction. it also showed that the target is not required to have conspicuous features and can be selected anywhere on natural rock surfaces excluding rock boundary and shadowed regions. the tracker was successfully executed on the opportunity rover near victoria crater on four distinct runs, including a single-sol instrument placement. we present the flight experiment data of the tracking performance and execution time. &copy; 2009 wiley periodicals, inc.
a multirange architecture for collision-free off-road robot navigation. we present a multilayered mapping, planning, and command execution system developed and tested on the lagr mobile robot. key to robust performance under uncertainty is the combination of a short-range perception system operating at high frame rate and low resolution and a long-range, adaptive vision system operating at lower frame rate and higher resolution. the short-range module performs local planning and obstacle avoidance with fast reaction times, whereas the long-range module performs strategic visual planning. probabilistic traversability labels provided by the perception modules are combined and accumulated into a robot-centered hyperbolic-polar map with a 200-m effective range. instead of using a dynamical model of the robot for short-range planning, the system uses a large lookup table of physically possible trajectory segments recorded on the robot in a wide variety of driving conditions. localization is performed using a combination of global positioning system, wheel odometry, inertial measurement unit, and a high-speed, low-complexity rotational visual odometry module. the end-to-end system was developed and tested on the lagr mobile robot and was verified in independent government tests. &copy; 2008 wiley periodicals, inc.
differentially constrained mobile robot motion planning in state lattices. we present an approach to the problem of differentially constrained mobile robot motion planning in arbitrary cost fields. the approach is based on deterministic search in a specially discretized state space. we compute a set of elementary motions that connects each discrete state value to a set of its reachable neighbors via feasible motions. thus, this set of motions induces a connected search graph. the motions are carefully designed to terminate at discrete states, whose dimensions include relevant state variables (e.g., position, heading, curvature, and velocity). the discrete states, and thus the motions, repeat at regular intervals, forming a lattice. we ensure that all paths in the graph encode feasible motions via the imposition of continuity constraints on state variables at graph vertices and compliance of the graph edges with a differential equation comprising the vehicle model. the resulting state lattice permits fast full configuration space cost evaluation and collision detection. experimental results with research prototype rovers demonstrate that the planner allows us to exploit the entire envelope of vehicle maneuverability in rough terrain, while featuring real-time performance. &copy; 2009 wiley periodicals, inc.
an autonomous rice transplanter guided by global positioning system and inertial measurement unit. this paper reports the development of an automated rice transplanter guided by a global positioning system and an inertia measurement unit using the controller area network bus. the actuator control command and data communication protocols comply with the iso 11783. the project aims to develop an autonomous agricultural system for operation in the paddy field. the automated rice transplanter presented in this paper is the first stage in achieving the project objective. this paper focuses on the development of sensor and main computer connections to the operating autonomous unit and the use of common control protocols for each of the automated machines. a simple steering control algorithm was used for straight traveling. the automated rice transplanter made a turn at the headland of the paddy field and moved to the next desired path. after 12 straight operations, the rms lateral deviation was observed to be less than 0.04 m and the rms heading angle error was less than 3.6 deg. &copy; 2009 wiley periodicals, inc.
ground verification of the feasibility of telepresent on-orbit servicing. in an ideal case telepresence achieves a state in which a human operator can no longer differentiate between an interaction with a real environment and a technical mediated one. this state is called transparent telepresence. the applicability of telepresence to on-orbit servicing (oos), i.e., an unmanned servicing operation in space, teleoperated from ground in real time, is verified in this paper. for this purpose, a communication test environment was set up on the ground, which involved the institute of astronautics (lrt) ground station in garching, germany, and the european space agency (esa) ground station in redu, belgium. both were connected via the geostationary esa data relay satellite artemis. utilizing the data relay satellite, a teleoperation was accomplished in which the human operator as well as the (space) teleoperator was located on the ground. the feasibility of telepresent oos was evaluated, using an oos test bed at the institute of mechatronics and robotics at the german aerospace center (dlr). the manipulation task was representative for oos and supported real-time feedback from the haptic-visual workspace. the tests showed that complex manipulation tasks can be fulfilled by utilizing geostationary data relay satellites. for verifying the feasibility of telepresent oos, different evaluation methods were used. the properties of the space link were measured and related to subjective perceptions of participants, who had to fulfill manipulation tasks. an evaluation of the transparency of the system, including the data relay satellite, was accomplished as well. &copy; 2009 wiley periodicals, inc.
a tele-experiment on rover motor control via internet. modern internet and multimedia techniques enable experiments with remote hardware. this way engineering students can gather practical experience even in areas where their own university does not have the related equipment in place. the focus of this paper is on an experiment to develop a motor controller for a remote mobile robot. implementation details of such an experiment are addressed with emphasis placed on the subject of tuning a pid controller for steering and speed adaptation of a rover. the complete experiment is conceived as a self-explaining learning unit on the web. the learning unit comprises material on theory, exercises to provide feedback to the student about his learning progress, simulations to study motor control effects, and finally the experiment with remote robot hardware. this paper presents software techniques to realize a robust system implementation, the educational considerations necessary to present the experiment material properly for the tele-education context, and experiences obtained during the use of this remote experiment in previously taught classes. &copy; 2005 wiley periodicals, inc.
manipulating deformable linear objects: sensor-based skills of adjustment motions for vibration reduction. the vibration of a deformable object is often problematic during automatic handling by robot manipulators. however, humans can often handle and damp the vibration of deformable objects with ease. this paper presents force&sol;torque sensor-based skills for handling deformable linear objects in a manner suitable to reduce acute vibration with simple human skill inspired strategies that consist of one or two adjustment motions. the adjustment motion is a simple open-loop motion that can be attached to the end of any arbitrary end-effector's trajectory. as an ordinary industrial robot's simple action, it has three periods, i.e., acceleration, constant speed, and deceleration period; it starts from a predicted time tightly close to a force&sol;moment maximum. the predicted time for the adjustment action is generated automatically on-line based on the vibration rhythm and the data sensed by a force&sol;torque sensor mounted on the robot's wrist. to find the matching point between the vibrational signal of the deformable object and a template, template matching techniques including cross-correlation and minimum squared error methods are used and compared. experiments are conducted with an industrial robot to test the new skills under various conditions. the results demonstrate that an industrial robot could perform effective vibration reduction skills with simple strategies. &copy; 2005 wiley periodicals, inc.
forces, activation and displacement prediction during free movement in the hand and forearm. this paper deals with the development of a highly realistic human hand and forearm model. the model contains 38 muscles and 24 degrees of freedom representing the joints of the system. the adopted model has to be as close as possible to the reality of the human being hand, to address several features linked to manipulation tasks, grasping objects and daily routine movements like shaving, writing, etc. in addition, a better comprehension of the biomechanical and neuromuscular behavior of the system is aimed. this will allow having a tool for the simulation of repairing surgery, acts such as tendon transfer. in this paper, we focus on the muscle forces determination for a given task. an optimization technique is used to resolve the redundant problem over the 24 joints of the system. also, a muscle model is used and is integrated in the optimization technique, in order to determine measurable values, like the activation and the displacement of each muscle in the system. the calculation is made during a real-time simulation. &copy; 2005 wiley periodicals, inc.
robot perception of impedance. this paper proposes an algorithm for robot perception of impedance, which can be used as a fundamental technique for real-time and qualitative perception of physical constraints imposed on the robot's end-effector. this algorithm (1) estimates the impedance that represents the motion-force relation of the end-effector; (2) calculates the uncertainties of the estimates; and (3) detects discontinuous changes in the impedance. the estimated impedance can be used to recognize local dynamic properties of the environment and temporary constraint conditions imposed on the end-effector. the detected discontinuities can be used to segment the manipulated tasks and to recognize the geometric structure of the environment. this method can be implemented in both autonomous and remote-controlled robots because it is designed separately from control methodologies. results of preliminary experiments are presented. &copy; 2005 wiley periodicals, inc.
the spatial conservative congruence transformation for manipulator stiffness modeling with coordinate and noncoordinate bases. this paper presents systematic methods to approach the spatial conservative congruence transformation (scct) and applies it to the stiffness transformation and matrices of robotic systems via the strategy of changing basis. through geometrical analysis, the realization of the cartesian stiffness of manipulators is shown to be basis dependent. we illustrate that the scct is conservative as well as directly represents the spatial stiffness mapping relationship for robotic stiffness control. examples of the serial manipulators are given to help one to better understand the source of the asymmetric 6&times;6 cartesian stiffness matrix in the presence of external loads using the scct algorithm. the scct suggests an explicit and generalized stiffness transformation relationship for robotic systems. &copy; 2005 wiley periodicals, inc. the acm portal is published by the association for computing machinery. copyright © 2010 acm, inc. terms of usage privacy policy code of ethics contact us useful downloads: adobe acrobat quicktime windows media player real player
2d map-building and localization in outdoor environments. determining the pose (position and orientation) of a vehicle at any time is termed localization and is of paramount importance in achieving reliable and robust autonomous navigation. knowing the pose it is possible to achieve high level tasks such as path planning. a new map-based algorithm for the localization of vehicles operating in harsh outdoor environments is presented in this article. a map building algorithm using observations from a scanning laser rangefinder is developed for building a polyline map that adequately captures the geometry of the environment. using this map, the iterative closest point (icp) algorithm is employed for matching laser range images from the rangefinder to the polyline map. once correspondences are established, an extended kalman filter (ekf) algorithm provides reliable vehicle state estimates using a nonlinear observation model based on the vertices of the polyline map. data gathered during field trials in an outdoor environment is used to test the efficiency of the proposed icp-ekf algorithm in achieving the localization of a four-wheel drive (4wd) vehicle. &copy; 2005 wiley periodicals, inc.