Distribution by Scientific Domains
Distribution within Engineering

Kinds of Robot

  • autonomous robot
  • mobile robot
  • surgical robot
  • wheeled mobile robot

  • Terms modified by Robot

  • robot arm
  • robot manipulator
  • robot navigation
  • robot system

  • Selected Abstracts


    M.A. Benayad
    ABSTRACT We present an open loop control design allowing to steer a wheeled mobile robot along a prespecified smooth geometric path, minimizing a given cost index and satisfying a set of dynamical constraints. Using the concept of "differential flatness," the problem is equivalent to the selection of the optimal time parametrization of the geometric path. This parametrization is characterized by a differential equation involving a function of the curvilinear coordinate along the path. For the minimum time problem, as well as for another index (such as the maximum value of the centripetal acceleration) to be minimized over a given time interval, the problem then reduces to the optimal choice of this function of the curvilinear coordinate. Using spline functions interpolation, the problem can be recast as a finite parameter optimization problem. Numerical simulation results illustrate the procedure. [source]

    Novel percutaneous catheter thrombectomy in acute massive pulmonary embolism: Rotational bidirectional thrombectomy (ROBOT)

    Masashi Yoshida MD
    Abstract Background: Although thrombolysis is a standard therapy in cases of pulmonary embolism (PE), fatal outcome is often observed. We designed and investigated the efficacy of a novel percutaneous catheter therapy, rotational bidirectional thrombectomy (ROBOT), for PE. Methods and Results: Eighteen patients with acute massive PE (Miller score , 20) were included in this study. We separated them into two groups [group A (n = 10), thrombolysis; group B (n = 8): thrombolysis and ROBOT or ROBOT alone]. There was no difference in the hemodynamic indices between the groups at diagnosis. ROBOT was designed to fragment emboli by rotating a regular pigtail catheter. Three deaths occurred in group A because of hemodynamic impairment, but there was no death in group B. One day after treatment, systolic pulmonary artery pressure had decreased from 53 ± 8 to 30 ± 8 mm Hg (P < 0.05) in group B and from 54 ± 5 to 42 ± 19 mm Hg (NS) in group A. The hospitalization period in group B was shorter than that in group A (17 ± 6 vs. 27 ± 10 days, P < 0.05). Conclusion: ROBOT therapy results in a significant, rapid improvement in the hemodynamic situation and in a better outcome than conventional therapy in patients with acute massive pulmonary embolism. © 2006 Wiley-Liss, Inc. [source]

    Design and power management of a solar-powered "Cool Robot" for polar instrument networks

    Laura E. Ray
    The Cool Robot is a four-wheel-drive, solar-powered, autonomous robot designed to support summertime science campaigns in Antarctica and Greenland over distances exceeding 500 km. This paper provides an overview of key features of the robot, including design for good mobility, high efficiency, and long-term deployment under solar power in harsh polar environments. The Cool Robot's solar panel box, comprising panels on four sides and a top panel, encounters insolation variations with a bandwidth of up to 1 Hz due to sastrugi. The paper details a unique photovoltaic control algorithm to accommodate these variations. We deployed the robot at Summit Camp, Greenland to validate its mobility and power budget and to assess the photovoltaic control system. The 61 kg robot drove continuously at 0.78 m/s on soft snow, its 160 W average power demand met by solar power alone under clear skies above 16° sun elevation. The power-control system reliably matched input with demand as insolation varied during testing. A simple GPS waypoint-following algorithm provides low-bandwidth path planning and course correction and demonstrated reliable autonomous navigation during testing over periods of 5,8 h. Field data validate the Cool Robot design models and indicate that it will exceed its design goal of carrying a 15 kg payload 500 km across Antarctica in 2 weeks. A brief description of instrument payloads and scientific studies aided by networks of such autonomous solar robots is provided. © 2007 Wiley Periodicals, Inc. [source]

    Design and Control of a Four-Wheeled Omnidirectional Mobile Robot with Steerable Omnidirectional Wheels

    Jae-Bok Song
    Omnidirectional mobile robots are capable of arbitrary motion in an arbitrary direction without changing the direction of wheels, because they can perform 3 degree-of-freedom (DOF) motion on a two-dimensional plane. In this research, a new class of omnidirectional mobile robot is proposed. Since it has synchronously steerable omnidirectional wheels, it is called an omnidirectional mobile robot with steerable omnidirectional wheels (OMR-SOW). It has 3 DOFs in motion and one DOF in steering. One steering DOF can function as a continuously variable transmission (CVT). CVT of the OMR-SOW increases the range of velocity ratio from the wheel velocities to robot velocity, which may improve performance of the mobile robot. The OMR-SOW with four omnidirectional wheels has been developed in this research. Kinematics and dynamics of this robot will be analyzed in detail. Various tests have been conducted to demonstrate the validity and feasibility of the proposed mechanism and control algorithm. © 2004 Wiley Periodicals, Inc. [source]

    Design of Statically Stable Walking Robot: A Review

    D. C. Kar
    The superior mobility characteristics of legged animals compared to those of wheeled or tracked vehicles for off-road locomotion motivated the development of artificial walking machines. The sustained worldwide efforts for the last few decades resulted in a large number of legged robots with different levels of sophistication. Here, various design approaches made so far to realize artificial legged locomotion are discussed. Mainly, different vehicle configurations as well as leg mechanisms which are already explored by researchers are reviewed in brief. The author hopes that this will serve as a brief account of previous research efforts and help future walking robot designers to develop more sophisticated machines. © 2003 Wiley Periodicals, Inc. [source]

    Application of a Service Climbing Robot with Motion Planning and Visual Sensing

    Jian Zhu
    This paper describes an application of a service climbing robot aimed to clean the glass wall of high-rise buildings. The robot utilizes suction cups to adhere to the glass and moves with a translational mechanism to follow a predetermined path in cleaning the whole glass surface. By a flexible waist, the robot can adjust its posture. The robot has the ability to cross the window frame to clean different sections of the glass wall. A visual sensing system, composed of an omnidirectional CCD camera and two laser diodes, enables the robot to measure its orientation and the distance between the robot and the window frame. The real-time applications and some experimental results demonstrate the effectiveness of the developed system. © 2003 Wiley Periodicals, Inc. [source]

    Aspects Regarding the Conception, Modeling and Implementation of an Articulated Robot in Space with Noises and Vibrations

    Virgil Ispas
    The authors want to conceive and to model a structure of a 6R serial modular industrial robot with six freedom degrees. Some specific points are followed: the direct geometric modelling of the robot using the matrix of rotation method, the given in 3D modelling of the robot, the presentation of its components having some possible applications in the processes of production in the spaces with noises and vibrations. The direct geometrical modelling will be determinate the relative orientation matrices, which express the position of each system Ti, (i=1-6), according to the system Ti,1, also expressing the vectors of relative position of origin Oi of the systems Ti. They will be expressed the orientation of each system Ti in account to the fixed system To attached to the robot base, the set of independent parameters of orientation then are obtained the final equation of the column vector of the generalized coordinates, which express the position and the orientation of the clamping device. The paper presents the two possible applications of the studied robot implementation in a flexible manufacturing cel for the manipulation operations of parts. The robot will be used on the other side for the execution of weld in a points applied to the car carcases. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Model Based Control of a Parallel Robot , A Comparison of Control Algorithms

    Hubert Hahn Prof. Dr.Article first published online: 25 MAR 200
    In this contribution the control behavior of a special construction of a parallel robot, called multi-axes test facility, is investigated. After a brief discussion of the different tasks of the robot the construction of the robot is briefly presented. To solve the tasks, different control algorithms are derived based on model equations of different complexity of the robot. Depending on the task to be performed by the robot, the controllers compensate the kinematic and/or kinetic coupling of the degrees of freedom of the robot, stabilize the system and achieve the desired spatial motion of each degree of freedom as well as sufficient robustness with respect to parameter uncertainties and load variations. A few results obtained in computer simulations and laboratory experiments are presented and judged with respect to the quality of control, the closeness to reality of the computer simulations, and the amount of costs and work needed to realize the different solutions. [source]

    Transoral Robotic Surgery: Supraglottic Laryngectomy in a Canine Model,

    THE LARYNGOSCOPE, Issue 7 2005
    Gregory S. Weinstein MD
    Abstract Objectives/Hypothesis: To develop a technique for computer enhanced robotic transoral supraglottic partial laryngectomy in the canine model. Study Design: Surgical procedure on the larynx in a canine model with a commercially available surgical robot. Methods: With use of the da Vinci Surgical Robot (Intuitive Surgical, Inc., Sunnyvale, CA), the supraglottic partial laryngectomy was performed on a mongrel dog that had been orotracheally intubated using general anesthesia. The videoscope and the 8 mm end-effectors of the robotic system were introduced through three ports, transorally. The surgical procedure was performed remotely from the robotic system console. The procedure was documented with still and video photography. Results: Supraglottic partial laryngectomy was successfully performed using the da Vinci Surgical Robot, with 8 mm instrumentation. The robotic system allowed for celerity and accuracy secondary to findings specific to the surgical approach, including excellent hemostasis, superb visualization of the operative field with expeditious identification of laryngeal submucosal soft tissue and skeletal landmarks, and multiplanar transection of tissues. In addition, the use of the robotic system also was found to have technical advantages inherent in robotic surgery, including the use of "wristed" instrumentation, tremor abolition, motion scaling, and three-dimensional vision. Conclusions: The da Vinci Surgical Robot allowed for successful robotic transoral supraglottic partial laryngectomy in the canine model. [source]

    Real-time deadlock-free navigation for multiple mobile robots

    Harunori Gakuhari
    Abstract This paper proposes a practicable navigation method for multiple mobile robots in a realistic environment. In the past, many navigation methods have been developed. However, they were often limited to a single robot and sometimes assumed robots with special mobility such as holonomic ones. From the viewpoint of practical applications it is indispensable that the number of robots is arbitrary and a general shape and mobility for them is allowed. In this study, deadlock-free navigation for nonholonomic mobile robots in a practical environment is given. In the proposed scheme, states of the environment and robots are fed back in real time, and global path planning is cyclically executed. This enables an adaptation to a changing environment and reliable, deadlock-free navigation for multiple robots. The real-time online path planning is performed by an efficient A* search in Configuration Spaces representing the robots and environment. The proposed method is tested in several simulations which represent typical complicated navigation situations. As a result, the effectiveness of the method is verified. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(3): 27, 36, 2008; Published online in Wiley InterScience ( DOI 10.1002/eej.20714 [source]

    Behavior selection of mobile robot based on integration of multimodal information

    Bin Chen
    Abstract Recently, biologically inspired robots have been developed to acquire the capacity for directing visual attention to salient stimulus generated from the audiovisual environment. For the purpose of realizing this behavior, a general method is to calculate saliency maps to represent how much the external information attracts the robot's visual attention, where the audiovisual information and robot's motion status should be involved. In this paper, we represent a visual attention model where three modalities,audio information, visual information, and robot's motor status,are considered, because previous research has not considered all of them. First, we introduce a 2D density map, on which the value denotes how much the robot pays attention to each spatial location. Then we model the attention density using a Bayesian network where the robot's motion statuses are involved. Next, the information from both audio and visual modalities is integrated with the attention density map in integrate-fire neurons. The robot can direct its attention to the locations where the integrate-fire neurons are fired. Finally, the visual attention model is applied to make the robot select the visual information from the environment, and react to the content selected. Experimental results show that it is possible for robots to acquire the visual information related to their behaviors by using the attention model considering motion statuses. The robot can select its behaviors to adapt to the dynamic environment as well as to switch to another task according to the recognition results of visual attention. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 39,48, 2007; Published online in Wiley InterScience ( DOI 10.1002/eej.20335 [source]

    Measurement of specific radioactivity in proteins separated by two-dimensional gel electrophoresis

    ELECTROPHORESIS, Issue 5-6 2006
    Shaobo Zhou
    Abstract We report a method to quantify the specific radioactivity of proteins that have been separated by 2-DE. Gels are stained with SyproRuby, and protein spots are excised. The SyproRuby dye is extracted from each spot using DMSO, and the fluorescence is quantified automatically using a plate reader. The extracted gel piece is then dissolved in hydrogen peroxide and radioactivity is quantified by liquid scintillation counting. Gentle agitation with DMSO for 24,h was found to extract all the SyproRuby dye from gel fragments. The fluorescence of the extract was linearly related to the amount of BSA loaded onto a series of 1-D gels. When rat muscle samples were run on 2-DE gels, the fluorescence extracted from 54,protein spots showed a good correlation (r = 0.79, p < 0.001) with the corresponding spot intensity measured by conventional scanning and image analysis. DMSO extraction was found not to affect the amount of radioactive protein left in the gel. When a series of BSA solutions of known specific radioactivity were run on 2-DE gels, the specific radioactivity measured by the new method showed a good correlation (r = 0.98, p < 0.01, n = 5) with the specific radioactivity measured directly before loading. Reproducibility of the method was measured in a series of 2-DE gels containing proteins from the livers of rats and mice that had been injected with [35S]methionine. Variability tended to increase when the amount of radioactivity in the protein spot was low, but for samples containing at least 10,dpm above background the CV was around 30%, which is comparable to that obtained when measuring protein expression by conventional image analysis of SyproRuby-stained 2-DE gels. Similar results were obtained whether spots were excised manually or using a spot excision robot. This method offers a high-throughput, cost-effective and reliable method of quantifying the specific radioactivity of proteins from metabolic labelling experiments carried out in,vivo, so long as sufficient quantities of radioactive tracer are used. [source]

    Endo-robotic resection of the submandibular gland in a cadaver model,

    David J. Terris MD
    Abstract Background. By means of a prospective, nonrandomized investigation, we evaluated the feasibility of performing endo-robotic resection of the submandibular gland in a cadaver model and compared the results of robotically enhanced endoscopic surgery with those from a conventional endoscopic technique. Methods. Procedural times were recorded in a consecutive series of 11 endoscopic submandibular gland resections using the daVinci Surgical System (Intuitive Surgical, Sunnyvale, CA) and a modified endoscopic surgical approach previously developed in a porcine model. The presence of neurovascular injury was assessed postoperatively, and the specimens were examined histologically. Results. Eleven endo-robotic submandibular gland resections were successfully performed in six cadavers (no conversions to open resection were necessary). The median duration of the procedures was 48 minutes (range, 33,82 minutes). Creation of the operative pocket took an average (±SD) of 12.2 ± 5.3 minutes, assembly of the robot required 9.3 ± 4.1 minutes, and the mean time for submandibular gland resection was 29.4 ± 8.9 minutes. The time required for robotic assembly was offset by the reduced operative time necessary compared with conventional endoscopic resection. Histologic examination confirmed the presence of normal glandular architecture, without evidence of excessive mechanical or thermal injury. There were no cases of apparent neurovascular injury. Conclusions. Robotically enhanced endoscopic surgery in the neck is feasible and offers a number of compelling advantages over conventional endoscopic neck surgery. Clinical trials will be necessary to determine whether these advantages can be achieved in clinical practice. © 2005 Wiley Periodicals, Inc. Head Neck27: XXX,XXX, 2005 [source]

    Ergonomics considerations and management action in the implementation of industrial robots

    Biman Das
    To obtain maximum benefit from the implementation of industrial robots, it is necessary to identify specific ergonomics problems and provide answers to such problems. Special features of a typical industrial robot are described. Specific ergonomics problems are identified and discussed: sociopsychological factors, systems safety design, communications, training, and workplace design. For the successful implementation of industrial robots, management should take timely action with regard to advanced planning procedures, user involvement plans, communication channels, company labor policies, and continuous training programs. The technological change from conventional to advanced manufacturing, such as industrial robots, must be jointly supported by all levels of management and workers. © 2001 John Wiley & Sons, Inc. [source]

    Solar power for an Antarctic rover

    J. H. Lever
    Abstract Sensors mounted on mobile robots could serve a variety of science missions in Antarctica. Although weather conditions can be harsh, Antarctic snowfields offer unique conditions to facilitate long-distance robot deployment: the absence of obstacles, firm snow with high albedo, and 24 h sunlight during the summer. We have developed a four-wheel-drive, solar-powered rover that capitalizes on these advantages. Analyses and field measurements confirm that solar power reflected from Antarctic snow contributes 30,40% of the power available to a robot consisting of a five-side box of solar panels. Mobility analyses indicate that the 80 kg rover can move at 0·8 m s,1 during clear sky conditions on firm snow into a 5 m s,1 headwind, twice the speed needed to achieve the design target of 500 km in 2 weeks. Local winter tests of the chassis demonstrated good grade-climbing ability and lower than predicted rolling resistance. Tests of the completed robot occurred in Greenland in 2005. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Can Infants Use a Nonhuman Agent's Gaze Direction to Establish Word,Object Relations?

    INFANCY, Issue 4 2009
    Laura O'Connell
    Adopting a procedure developed with human speakers, we examined infants' ability to follow a nonhuman agent's gaze direction and subsequently to use its gaze to learn new words. When a programmable robot acted as the speaker (Experiment 1), infants followed its gaze toward the word referent whether or not it coincided with their own focus of attention, but failed to learn a new word. When the speaker was human, infants correctly mapped the words (Experiment 2). Furthermore, when the robot interacted contingently, this did not facilitate infants' word mapping (Experiment 3). These findings suggest that gaze following upon hearing a novel word is not sufficient to learn the referent of the word when the speaker is nonhuman. [source]

    Shared challenges in object perception for robots and infants

    Paul Fitzpatrick
    Abstract Robots and humans receive partial, fragmentary hints about the world's state through their respective sensors. These hints,tiny patches of light intensity, frequency components of sound, etc.,are far removed from the world of objects which we feel and perceive so effortlessly around us. The study of infant development and the construction of robots are both deeply concerned with how this apparent gap between the world and our experience of it is bridged. In this paper, we focus on some fundamental problems in perception which have attracted the attention of researchers in both robotics and infant development. Our goal was to identify points of contact already existing between the two fields, and also important questions identified in one field that could fruitfully be addressed in the other. We start with the problem of object segregation: how do infants and robots determine visually where one object ends and another begins? For object segregation, both the fields have examined the idea of using ,key events' where perception is in some way simplified and the infant or robot acquires knowledge that can be exploited at other times. We propose that the identification of the key events themselves constitutes a point of contact between the fields. Although the specific algorithms used in robots do not necessarily map directly to infant strategies, the overall ,algorithmic skeleton' formed by the set of algorithms needed to identify and exploit key events may in fact form the basis for mutual dialogue. We then look more broadly at the role of embodiment in humans and robots, and see the opportunities it affords for development. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    A fractional adaptation law for sliding mode control

    Mehmet Önder Efe
    Abstract This paper presents a novel parameter tuning law that forces the emergence of a sliding motion in the behavior of a multi-input multi-output nonlinear dynamic system. Adaptive linear elements are used as controllers. Standard approach to parameter adjustment employs integer order derivative or integration operators. In this paper, the use of fractional differentiation or integration operators for the performance improvement of adaptive sliding mode control systems is presented. Hitting in finite time is proved and the associated conditions with numerical justifications are given. The proposed technique has been assessed through a set of simulations considering the dynamic model of a two degrees of freedom direct drive robot. It is seen that the control system with the proposed adaptation scheme provides (i) better tracking performance, (ii) suppression of undesired drifts in parameter evolution, (iii) a very high degree of robustness and improved insensitivity to disturbances and (iv) removal of the controller initialization problem. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Adaptive motion/force tracking control of holonomic constrained mechanical systems: a unified viewpoint

    Chian-Song Chiu
    Abstract This paper proposes a robust adaptive motion/force tracking controller for holonomic constrained mechanical systems with parametric uncertainties and disturbances. First, two types of well-known holonomic systems are reformulated as a unified control model. Based on the unified control model, an adaptive scheme is then developed in the presence of pure parametric uncertainty. The proposed controller guarantees asymptotic motion and force tracking without the need of extra conditions. Next, when considering external disturbances, control gains are designed by solving a linear matrix inequality (LMI) problem to achieve prescribed robust performance criterion. Indeed, arbitrary disturbance/parametric error attenuation with respect to both motion and force errors along with control input penalty are ensured in the L2 -gain sense. Finally, applications are carried out on a two-link constrained robot and two planar robots transporting a common object. Numerical simulation results show the expected performances. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Repetitive control of synchronized operations for process applications

    James D. Ratcliffe
    Abstract Repetitive control (RC) algorithms for a plant, which contain pairs of complex conjugate poles at low frequency, resulting in a resonant system, is the subject area of this paper where the experimental results given are for a gantry robot and conveyor system in which the gantry is required to transfer payloads to a constant velocity conveyor by performing a repeating ,pick and place' operation. Initially, the gantry robot is controlled by means of a PID feedback controller in parallel with a proportional (P-type) repetitive feed-forward loop, while the conveyor operates under proportional feedback control. It is found that the RC system is unable to achieve long-term performance. The performance degrades within a relatively small number of repetitions due to the build up of resonant frequencies in the learning loop. To prevent this, a batch aliasing technique, originally developed for iterative learning control, is modified to work in the RC framework, and is implemented in real-time. The superior performance potential of the aliasing system is demonstrated experimentally. In the second part of this paper, multi-machine systems, are considered where the critical new factor is the relative error between the conveyor and the robot. Here a second supervisory learning loop is proposed for use to shift the reference trajectory of one machine so that the relative placement error is also reduced. Again, supporting experimental results are given. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Robot vision with cellular neural networks: a practical implementation of new algorithms

    Giovanni Egidio Pazienza
    Abstract Cellular neural networks (CNNs) are well suited for image processing due to the possibility of a parallel computation. In this paper, we present two algorithms for tracking and obstacle avoidance using CNNs. Furthermore, we show the implementation of an autonomous robot guided using only real-time visual feedback; the image processing is performed entirely by a CNN system embedded in a digital signal processor (DSP). We successfully tested the two algorithms on this robot. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Guiding a mobile robot with cellular neural networks

    Xavier Vilasís-Cardona
    Abstract We show how cellular neural networks (CNNs) are capable of providing the necessary signal processing needed for visual navigation of an autonomous mobile robot. In this way, even complex feature detection and object recognition can be obtained in real time by analogue hardware, making fully autonomous real-time operation feasible. An autonomous robot was first simulated and then implemented by simulating the CNN with a DSP. The robot is capable of navigating in a maze following lines painted on the floor. Images are processed entirely by a CNN-based algorithm, and navigation is controlled by a fuzzy-rule-based algorithm. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Multi-template approach to realize central pattern generators for artificial locomotion control

    Paolo Arena
    Abstract Biologically inspired control of artificial locomotion often makes use of the concept of central pattern generator (CPG), a network of neurons establishing the locomotion pattern within a lattice of neural activity. In this paper a new approach, based on cellular neural networks (CNNs), for the design of CPGs is presented. From a biological point of view this new approach includes an approximated chemical synapse realized and implemented in a CNN structure. This allows to extend the results, previously obtained with a reaction-diffusion-CNN (RD-CNN) for the locomotion control of a hexapod robot, to a more general class of artificial CPGs in which the desired locomotion pattern and the switching among patterns are realized by means of a spatio-temporal algorithm implemented in the same CNN structure. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Learning weighted linguistic rules to control an autonomous robot

    M. Mucientes
    A methodology for learning behaviors in mobile robotics has been developed. It consists of a technique to automatically generate input,output data plus a genetic fuzzy system that obtains cooperative weighted rules. The advantages of our methodology over other approaches are that the designer has to choose the values of only a few parameters, the obtained controllers are general (the quality of the controller does not depend on the environment), and the learning process takes place in simulation, but the controllers work also on the real robot with good performance. The methodology has been used to learn the wall-following behavior, and the obtained controller has been tested using a Nomad 200 robot in both simulated and real environments. © 2009 Wiley Periodicals, Inc. [source]

    Integrating fuzzy topological maps and fuzzy geometric maps for behavior-based robots

    Eugenio Aguirre
    In behavior-based robots, planning is necessary to elaborate abstract plans that resolve complex navigational tasks. Usually maps of the environment are used to plan the robot motion and to resolve the navigational tasks. Two types of maps have been mainly used: metric and topological maps. Both types present advantages and weakness so that several integration approaches have been proposed in literature. However, in many approaches the integration is conducted to build a global representation model, and the planning and navigational techniques have not been fitted to profit from both kinds of information. We propose the integration of topological and metric models into a hybrid deliberative-reactive architecture through a path planning algorithm based on A* and a hierarchical map with two levels of abstraction. The hierarchical map contains the required information to take advantage of both kinds of modeling. On one hand, the topological model is based on a fuzzy perceptual model that allows the robot to classify the environment in distinguished places, and on the other hand, the metric map is built using regions of possibility with the shape of fuzzy segments, which are used later to build fuzzy grid-based maps. The approach allows the robot to decide on the use of the most appropriate model to navigate the world depending on minimum-cost and safety criteria. Experiments in simulation and in a real office-like environment are shown for validating the proposed approach integrated into the navigational architecture. © 2002 Wiley Periodicals, Inc. [source]

    Deployment algorithms for a power-constrained mobile sensor network

    Andrew Kwok
    Abstract This paper presents distributed coverage algorithms for mobile sensor networks in which agents have limited power to move. Rather than making use of a constrained optimization technique, our approach accounts for power constraints by assigning non-homogeneously time-varying regions to each robot. This leads to novel partitions of the environment into limited-range, generalized Voronoi regions. The motion control algorithms are then designed to ascend the gradient of several types of locational optimization functions. In particular, the objective functions reflect the global energy available to the group and different coverage criteria. As we discuss in the paper, this has an effect on limiting each agent's velocity to save energy and balance its expenditure across the network. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    Robust discontinuous exponential regulation of dynamic nonholonomic wheeled mobile robots with parameter uncertainties

    B. L. Ma
    Abstract For regulating a dynamic nonholonomic WMR (wheeled mobile robot) with parameter uncertainties, we derive a simple robust discontinuous control law, yielding a global exponential convergence of position and orientation to the desired set point despite parameter uncertainties. The controller design relies on separating the error dynamics into two subsystems, followed by robust feedback control laws to stabilize the subsystems. The effectiveness of the proposed control laws is verified by simulation. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    Nonsingular path following control of a unicycle in the presence of parametric modelling uncertainties

    L. Lapierre
    Abstract A new type of control law is derived to steer the dynamic model of a wheeled robot of unicycle type along a desired path. The methodology adopted for path following control deals explicitly with vehicle dynamics and plant parameter uncertainty. Furthermore, it overcomes stringent initial condition constraints that are present in a number of path following control strategies described in the literature. This is done by controlling explicitly the rate of progression of a ,virtual target' to be tracked along the path, thus bypassing the problems that arise when the position of the virtual target is simply defined by the projection of the actual vehicle on that path. In the paper, a nonlinear adaptive control law is derived that yields convergence of the (closed-loop system) path following error trajectories to zero. Controller design relies on Lyapunov theory and backstepping techniques. Simulation results illustrate the performance of the control system proposed. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Autolabo: an automated system for ligand-soaking experiments with protein crystals

    Michihiro Sugahara
    Ligand soaking of protein crystals is important for the preparation of heavy-atom derivative crystals for experimental phasing as well as for large-scale ligand screening in pharmaceutical developments. To facilitate laborious large-scale ligand screening, to reduce the risk of human contact with hazardous ligand reagents and to increase the success rate of the soaking experiments, a protein crystallization robot `Autolabo' has been developed and implemented in the high-throughput crystallization-to-structure pipeline at RIKEN SPring-8 Center. The main functions of this robotic system are the production of protein crystals for experiments, the ligand soaking of these crystals and the observation of soaked crystals. The separate eight-channel dispensers of Autolabo eliminate the cross-contamination of reagents which should be strictly avoided in the ligand-soaking experiment. Furthermore, the automated approach reduces physical damage to crystals during experiments when compared with the conventional manual approach, and thereby has the potential to yield better quality diffraction data. Autolabo's performance as a ligand-soaking system was evaluated with a crystallization experiment on ten proteins from different sources and a heavy-atom derivatization experiment on three proteins using a versatile cryoprotectant containing heavy-atom reagents as ligands. The crystallization test confirmed reliable crystal reproduction in a single condition and the capability for crystallization with nucleants to improve crystal quality. Finally, Autolabo reproducibly derivatized the test protein crystals with sufficient diffraction quality for experimental phasing and model building, indicating a high potentiality of this automated approach in ligand-soaking experiments. [source]

    A 100-position robotic sample changer for powder diffraction with low-background vacuum chamber

    S. R. Olsen
    At the new Australian OPAL research reactor, experiments carried out at room temperature use a substantial fraction of beam time on the high-resolution powder diffractometer, Echidna. With an average data collection time of 2,h and a complicated safety interlock system to protect users, the need for a fully automated and remotely controlled system was quickly realized. This report presents a solution based on a commercial four-axis robot capable of loading samples from two 50-position sample trays, in any order, into an automatically evacuated chamber. This chamber significantly reduced background signal arising from air scattering, with the effect being especially pronounced at low and high 2, angles. In the case of textured or inhomogeneous samples, the system may be re-configured so that the robot rotates the sample in the beam or translates it vertically through the beam. [source]