waashk/dblp huggingface dataset:
optimal byzantine-resilient convergence in uni-dimensional robot networks. given a set of robots with arbitrary initial location and no agreement on a global coordinate system, convergence requires that all robots asymptotically approach the exact same, but unknown beforehand, location. robots are oblivious-they do not recall the past computations-and are allowed to move in a one-dimensional space. additionally, robots cannot communicate directly, instead they obtain system related information only via visual sensors. even though convergence and the classical distributed approximate agreement problem (that requires correct processes to decide, for some constant @e, values distance @e apart and within the range of initial proposed values) are similar, we provide evidence that solving convergence in robot networks requires specific assumptions about synchrony and byzantine resilience. in more detail, we prove necessary and sufficient conditions for the convergence of mobile robots despite a subset of them being byzantine (i.e. they can exhibit arbitrary behavior). additionally, we propose two deterministic convergence algorithms for robot networks and analyze their correctness and complexity in various atomicity and synchrony settings. the first algorithm tolerates f byzantine robots for (2f+1)-sized robot networks in fully synchronous atom networks, while the second proposed algorithm tolerates f byzantine robots for (3f+1)-sized robot networks in non-atomic corda networks. the resilience of these two algorithms is proved to be optimal.
contract-based discovery of web services modulo simple orchestrators. web services are distributed processes exposing a public description of their behavior, or contract. the availability of repositories of web service descriptions enables interesting forms of dynamic web service discovery, such as searching for web services having a specified contract. this calls for a formal notion of contract equivalence satisfying two contrasting goals: being as coarse as possible so as to favor web services reuse, and guaranteeing successful client/service interaction. we study an equivalence relation that achieves both goals under the assumption that client/service interactions may be mediated by simple orchestrators. in the framework we develop, orchestrators play the role of proofs (in the curry-howard sense) justifying an equivalence relation between contracts. this makes it possible to automatically synthesize orchestrators out of web services contracts.
the parameterized complexity of editing graphs for bounded degeneracy. we examine the parameterized complexity of the problem of editing a graph to obtain an r-degenerate graph. we show that for the editing operations vertex deletion and edge deletion, both separately and combined, the problem is w[p]-complete, and remains w[p]-complete even if the input graph is already (r+1)-degenerate, or has maximum degree 2r+1 for all r>=2. we also demonstrate fixed-parameter tractability for several clique based problems when the input graph has bounded degeneracy.
computational complexity of long paths and cycles in faulty hypercubes. the problem of existence of an optimal-length (long) fault-free cycle in the n-dimensional hypercube with f faulty vertices is np-hard. this holds even in case that f is bounded by a polynomial of degree three (six) with respect to n. on the other hand, there is a linear (quadratic) bound on f which guarantees that the problem is decidable in polynomial time. similar results are obtained for paths as well as for paths between prescribed endvertices.
n-player partizan games. conway's theory of partizan games is both a theory of games and a theory of numbers. an extension of this theory to classify partizan games with an arbitrary finite number of players is presented.
port-based modeling and simulation of mechanical systems with rigid and flexible links. in this paper, a systematic procedure for the definition of the dynamical model in port-hamiltonian form of mechanical systems is presented as the result of the power-conserving interconnection of a set of basic components (rigid bodies, flexible links, and kinematic pairs). since rigid bodies and flexible links are described within the port-hamiltonian formalism, their interconnection is possible once a proper relation between the power-conjugated port variables is deduced. these relations are the analogous of the kirchhoff laws of circuit theory. from the analysis of a set of oriented graphs that describe the topology of the mechanism, an automatic procedure for deriving the dynamical model of a mechanical system is illustrated. the final model is a mixed port-hamiltonian system, because of the presence of a finite-dimensional subsystem (modeling the rigid bodies) and an infinite-dimensional one (describing the flexible links). besides facilitating the deduction of the dynamical equations, it is shown howthe intrinsic modularity of this approach also simplifies the simulation phase.
nonlinear and filtered force/position mappings in bilateral teleoperation with application to enhanced stiffness discrimination. motivated by applications involving soft-tissue manipulation such as robotic surgery, the transparency objectives in bilateral teleoperation are redefined to include monotonic non-linear and linear-time-invariant filter mappings between the master/slave position and force signals. to demonstrate the utility of the new performance measures, a stiffness discrimination telemanipulation task of soft environments is considered. a nonlinear force mapping can enhance stiffness discrimination thresholds as shown through a set of psychophysics experiments.lyapunov-based adaptive motion/force controllers are presented that can achieve the new transparency objectives in the presence of dynamic uncertainty in the master, slave, user, and environment and in the absence of time delay. given a priori known bounds on unknown dynamic parameters, a framework for robust stability analysis is proposed that uses an off-axis circle criterion and the nyquist envelope of interval plant systems. nonlinear- and linear-filtered mappings are achieved in experiments with a two-axis teleoperation system.
dynamic manipulation inspired by the handling of a pizza peel. this paper discusses dynamic manipulation inspired by the handling mechanism of a pizza chef. the chef handles a tool called "pizza peel," where a plate is attached at the tip of a bar, and he remotely manipulates a pizza on the plate. we found that he aggressively utilizes only two degrees of freedom (dofs) from the remote handling location during manipulation: translation along the bar and rotation about the bar. from the viewpoint of a dynamic system, the inertial loads for these specific dofs are never affected by the length of the bar. this is important for the production of quick plate motions so that the object on the plate can be dynamically and remotely manipulated. applying this handling mechanism to a robot system, we first reveal how tomake the object's motion for three dofs by using two dofs of platemotion. we then show that it is guaranteed to achieve an arbitrary desired set of position and orientation of the object by the proposed manipulation scheme. the proposed method has good manipulability because the translational motion of the object can be fully decoupled from the rotational motion (though not vice versa). finally, we show a couple of experiments that confirm the basic idea.
improving the human-robot interface through adaptive multispace transformation. teleoperation is essential for applications in which, despite the availability of a precise geometrical definition of the working area, a task cannot be explicitly programmed. this paper describes a method of assisted teleoperation that improves the execution of such tasks in terms of ergonomics, precision, and reduction of execution time. the relationships between the operating spaces corresponding to the human-robot interface triangle are analyzed. the proposed teleoperation aid is based on applying adaptive transformations between these spaces.
swarmorph: multirobot morphogenesis using directional self-assembly. in this paper, we propose swarmorph: a distributed morphology generation mechanism for autonomous self-assembling mobile robots. self-organized growth of global morphological structures emerges through the repeated application of local morphology extension rules. we present details of the directional self-assembly mechanism that provides control over the orientation of interrobot connections. we conduct realworld experiments to validate the low-level directional self-assembly mechanism and the growth of global morphologies. we demonstrate the scalability of the approach with large numbers of robots in simulation-based experiments.
fast generation of multiple collision-free and linear trajectories in dynamic environments. a fast and complete collision-detection procedure is presented in this paper. given a straight-line path for a mobile robot, the current instant of time, and estimations of the obstacles motions, a set of speeds is obtained in real time with neither space nor time discretization. the mobile-robot path together with each one of these speeds, if they exist, states a different collision-free trajectory. all these trajectories verify that the minimum distance between the mobile robot and the obstacles at anytime is greater than or equal to a configurable parameter. this set of speeds is fast updated when a change in the original mobile-robot path is considered. if the current mobile-robot speed does not belong to the mentioned set of speeds, then the mobile robot will collide with at least one obstacle and, in this case, a set of accelerations is fast-tuned to avoid all the obstacles. collision-free trajectories that do not verify the dynamic constraints of the mobile robot are simply rejected.
increasing accuracy in image-guided robotic surgery through tip tracking and model-based flexion correction. robot assistance can enhance minimally invasive image-guided surgery, but flexion of the thin surgical instrument shaft impairs accurate control by creating errors in the kinematic model. two controller enhancements that can mitigate these errors are improved kinematic models that account for flexing and direct measurement of the instrument tip's position. this paper presents an experiment quantifying the benefits of these enhancements in an effort to inform development of an image-guided robot control system accurate in the presence of quasi-static instrument flexion. the study measured a controller's ability to guide a flexing instrument along user-commanded motions while preventing incursions into a forbidden region virtual fixture. compared with the controller using neither enhancement, improved kinematics and reduced maximum incursion depth into the forbidden region by 28%, tip tracking by 67%, and both enhancements together by 83%.
global output tracking control of flexible joint robots via factorization of the manipulator mass matrix. this paper investigates the problem of global output feedback tracking control of flexible joint robots. despite the fact that only link position and actuator position are available from measurements, the proposed controller ensures that the link position globally tracks the desired trajectory while keeping all the remaining signals bounded. the controller development uses a partial state-feedback linearization technique combined with the integrator backstepping control design method whereas a filter and an observer are utilized to remove the requirement of link and actuator velocity measurements. partial state-feedback linearization of robot dynamics is performed by factoring the manipulator mass matrix into a quadratic form involving an integrable root matrix. the applicability of the proposed general design methodology is illustrated by an example of flexible joint planar robots. numerical results for a two-link flexible joint planar robot are also provided.
automatic camera-based microscope calibration for a telemicromanipulation system using a virtual pattern. in the context of virtualized-reality-based telemicromanipulation, this paper presents a visual calibration technique for an optical microscope coupled to a charge-coupled device (ccd) camera. the accuracy and flexibility of the proposed automatic virtual calibration method, based on parallel single-plane properties, are outlined. in contrast to standard approaches, a 3-d virtual calibration pattern is constructed using the micromanipulator tip with subpixel-order localization in the image frame. the proposed procedure leads to a linear system whose solution provides directly both the intrinsic and extrinsic parameters of the geometrical model. computer simulations and real data have been used to test the proposed technique, and promising results have been obtained. based on the proposed calibration techniques, a 3-d virtual microenvironment of the workspace is reconstructed through the real-time imaging of two perpendicular optical microscopes. our method provides a flexible, easy-to-use technical alternative to the classical techniques used in micromanipulation systems.
velocity-scheduling control for a unicycle mobile robot: theory and experiments. improvement over classical dynamic feedback linearization for a unicycle mobile robots is proposed. compared to classical extension, the technique uses a higher-dimensional state extension, which allows rejecting a constant disturbance on the robot rotational axis. the proposed dynamic extension acts as a velocity scheduler that specifies, at each time instant, the ideal translational velocity that the robot should have. by using a higher-order extension, both the magnitude and the orientation of the velocity vector can be generated, which introduces robustness in the control scheme. stability for both asymptotic convergence to a point and trajectory tracking is proven. the theoretical results are illustrated first in simulation, and then experimentally on the autonomous mobile robot fouzy iii.
identification of contact dynamics parameters for stiff robotic payloads. this paper investigates and demonstrates the feasibility of identifying contact dynamics parameters for stiff robotic payloads using a robotic system. the contact dynamics model for stiff payloads is motivated, and theoretical parameter values and bounds are provided. then, the effect of nonidealities such as surface roughness and plastic deformation on the theoretical values is demonstrated. a row-wise-scaled total least-squares parameter estimation algorithm is proposed and applied to experimental data measured using the special purpose dexterous manipulator task verification facility manipulator at the canadian space agency. the experimental results are compared to a separate set of experiments with a material testing machine as well as finite-element modeling results. finally, the experimental findings are generalized by providing guidelines for the maximum identifiable payload stiffness as a function of the position resolution, the maximum exertable force, and the structural stiffness of the robotic system.
kinematic modeling and analysis of skid-steered mobile robots with applications to low-cost inertial-measurement-unit-based motion estimation. skid-steered mobile robots are widely used because of their simple mechanism and high reliability. understanding the kinematics and dynamics of such a robotic platform is, however, challenging due to the complex wheel/ground interaction and kinematic constraints. in this paper, we develop a kinematic modeling scheme to analyze the skid-steered mobile robot. based on the analysis of the kinematics of the skid-steered mobile robot, we reveal the underlying geometric and kinematic relationships between the wheel slips and locations of the instantaneous rotation centers. as an application example, we also present how to utilize the modeling and analysis for robot positioning and wheel slip estimation using only low-cost strapdown inertial measurement units. the robot positioning and wheel slip-estimation scheme is based on an extended kalman filter (ekf) design that incorporates the kinematic constraints for accuracy enhancement. the performance of the ekf-based positioning and wheel slip-estimation scheme are also presented. the estimation methodology is tested and validated experimentally on a robotic test bed.
configuration tracking for continuum manipulators with coupled tendon drive. robotic control of flexible devices can enhance and simplify many medical procedures. we present a method for controlling a tendon-driven continuum manipulator by means of specifying the shape configuration. the basis for control is a linear beam configuration model that transforms beam configuration to tendon displacement by modeling internal loads of the compliant system. an essential aspect of this model is the inclusion of both themechanical and geometrical coupling among serial articulating sections. important capabilities of this model are the general forward kinematics and the decoupled inverse kinematics that allow for independent control of multiple sections. tracking results are presented for a cardiac catheter with two articulating sections.
a sensor-based controller for homing of underactuated auvs. a new sensor-based homing integrated guidance and control law is presented to drive an underactuated autonomous underwater vehicle (auv) toward a fixed target, in three dimensions, using the information provided by an ultrashort baseline (usbl) positioning system. the guidance and control law is first derived using quaternions to express the vehicle's attitude kinematics, which are directly obtained from the time differences of arrival (tdoa) measured by the usbl sensor. the dynamics are then included resorting to backstepping techniques. the proposed lyapunov based control law yields global asymptotic stability in the absence of external disturbances and is further extended, keeping the same properties, to the case where constant known ocean currents affect the dynamics of the vehicle. finally, a globally exponentially stable nonlinear tdoa and range-based observer is introduced to estimate the ocean current and uniform asymptotic stability is obtained for the overall closed-loop system. simulations are presented illustrating the performance of the proposed solutions.
shortest paths to obstacles for a polygonal dubins car. in this paper, we characterize the time-optimal trajectories leading a dubins car in collision with the obstacles in its workspace. due to the constant velocity constraint characterizing the dubins car model, these trajectories form a sufficient set of shortest paths between any robot configuration and the obstacles in the environment.based on these paths, we define and give the algorithm for computing a distance function that takes into account the nonholonomic constraints and captures the nonsymmetric nature of the system. the developments presented here assume that the obstacles and the robot are polygons although the methodology can be applied to different shapes.
interpersonal synchronization of body motion and the walk-mate walking support robot. everyone has probably experienced the phenomenon where their footsteps unconsciously synchronize with their partner while walking together. this interpersonal synchronization of body motion has been widely observed and is significant in the context of social psychology. however, the mechanism of this embodied cooperation still remains obscure and has not been substantially developed as an engineering application. in this study, by assuming "mutual entrainment" as an interpersonal synchronization mechanism, we establish a new cooperative walking system between a walking human and a walking robot (an agent as a virtual robot). in this system, rhythmic sounds corresponding to the timing of footsteps are exchanged between them on the basis of our previous studies. as a result, it was demonstrated that the two walking rhythms adapt mutually after the start of interaction, and stable synchronization is generated automatically. this global entrained state exhibits dynamic stability with small fluctuation in the walking period. applying this method to walking support for parkinson's disease and hemiplegia patients, its effectiveness in stabilizing the walking of the patient was shown. these results indicate the importance of interpersonal mutual entrainment of rhythmic motion for walking support, and new human-robot interaction technologies are expected as an extension of this framework.
nonlinear feedback control of a gravity-assisted underactuated manipulator with application to aircraft assembly. a nonlinear feedback scheme for a gravity-assisted underactuated manipulator with second-order nonholonomic constraints is presented in this paper. the joints of the hyper articulated arm have no dedicated actuators but are activated by gravity. by tilting the base link appropriately, the gravitational torque drives the unactuated links to a desired angular position.with simple locking mechanisms, the hyperarticulated arm can change its configuration using only one actuator at the base. this underactuated arm designwas motivated by the need for a compact snakelike robot that can go into aircraft wings and perform assembly operations using heavy end-effectors. the dynamics of the unactuated links are essentially second-order nonholonomic constraints for which there are no general methods to design closed-loop control. we propose a nonlinear closed-loop control law that is guaranteed to be stable in positioning one unactuated joint at a time. we synthesize a lyapunov function to prove the convergence of this control scheme. the lyapunov function also generates estimates of the domain of convergence of the control law for various control gains. the control algorithm is implemented on a prototype three-link system. finally, we provide some experimental results to demonstrate the efficacy of the control scheme.
vision-aided inertial navigation for spacecraft entry, descent, and landing. in this paper, we present the vision-aided inertial navigation (visinav) algorithm that enables precision planetary landing. the vision front-end of the visinav system extracts 2-d-to- 3-d correspondences between descent images and a surface map (mapped landmarks), as well as 2-d-to-2-d feature tracks through a sequence of descent images (opportunistic features). an extended kalman filter (ekf) tightly integrates both types of visual feature observations with measurements from an inertial measurement unit. the filter computes accurate estimates of the lander's terrain-relative position, attitude, and velocity, in a resource-adaptive and hence real-time capable fashion. in addition to the technical analysis of the algorithm, the paper presents validation results from a sounding-rocket test flight, showing estimation errors of only 0.16 m/s for velocity and 6.4 m for position at touchdown. these results vastly improve current state of the art for terminal descent navigation without visual updates, and meet the requirements of future planetary exploration missions.